AA Buffs
These buffs are extremely useful and in my opinion some of our better buffs come from AA. Here is a nice list of buffs that you can get from AA.
Don’t Kill the Messenger
Increases all crit chances by 7.5%. This is a must for pretty much all round gameplay. Having 30% crit total for 24 levels of AA is probably the best we have proportionally.
Fortissimo
15% melee and ranged DA(with skald's striking, TSO dirge line). This to me is one of my most useful buffs, being almost always in a melee group. I cannot see myself ever playing without it. 15% all round DA is pretty sweet and most dirges would say it is a must have.
Heroic Storytelling
Taken out of the dictionary for renevations...ie useless crap

thought I would clarify that...
Luck of the Dirge
This is something that again pretty much all dirges have. It increases all trigger percentages by 20% of your current %age. Since we have a lot of triggers with TSO etc, it is quite handy to have this and the T2 TSO BP, which adds 30% proc chance to CoB, so if you have absolutely nothing boosting your CoB it will be on 20% of the time meaning even with just that time period it would be useful to have

.
Please Note, this is on top of current percentage ie 20% proc goes up to 24% proc.
Allegro
Increases Casting Speed of group members by x amount. This is handy for any player as they all have to cast something. To get DKTM you should get this, it is possible to get DKTM without it, but this is the most efficient points you will spend on the way to it.
Dexterous Sonata
This increases all of your base critical multipliers. A lot of people havent heard of these, so here's a run down. Your Base critical multiplier is how much your attack does when you land a critical, and this is default 30% (or 1.3). Increasing your critical multipliers by 10% puts them up to 1.4. This will increase your dps generally by 0.5 * dps * 0.(crit percent) * 1.(DA chance) * 1.(new critical multiplier) all divided by 1.3.
Battle Cry
Increases Melee + Ranged DA by 15% and flurry by 5% of a single group friend. This cannot be yourself (/cries). Although this is useful to use on either a tank struggling to keep aggro or a scout-type in your group (I would class brawlers as scout type in this instance). You are supposed to need 182 AA to get this but can be got at 172, with a heck of a lot of platinum down the drain. I would personally get to 177 with 7 points in the dirge line and then respec a different tree to put 7 more points in the dirge line, I'm pretty sure most people are familiar with that trick.
AA Abilities
Bard Tree
STR
The STR line contains mainly AE blocker(personal and goup), avoidance buff increase and attribute buff increase. This is often called spacker spec in my books, as we only need it in raids when your GL has requested it.
AGI
The STR line contains bump (most dirges get this so they can use both stealth attacks), a parry + absorb passive, and a poison proc (not to mention vanishing act, which basically allows your group to dodge the next attack)
STA
The STA line contains a knockback for when you use a roundshield, a passive block chance and DA increase, a group buff that increases all around DA and a 100% chance to block the next attack with your shield.
WIS
The WIS line consists of a ranged attack, an increase to your speed buff, a casting speed group buff and DKTM which increases all crit chances by 7.5%.
INT
The INT line has rhythm blade that increases your ord/mini/subj/dist/focus/pierce/slash for 30 seconds, a combat skills/casting technique buff increase, attack speed/dps increase and HO effectiveness inrease.
Dirge Tree
Degradations
Basically makes your debuffs better debuffs. The end one increases duration/casting speed of green debuffs and reduces power cost.
Control
Improves reuse speed of a few abilities and adds a chance to our AE stun. The end line ability makes a mob select a target that is scout/fighter. This ability can be fun
Life and Death
Increases our heals and reduces some power costs and reduces health cost of our main heal. End line ability increases the targets mana/hp regen in combat by 50% so long as they are still under the effects of a ressurretion spell.
Luck
Basically improves a handful of spells in different ways such as more proc chance on dead calm, longer duration on CoB etc. End ability increases proc chances by 20%.
Shadows Tree
General
Basically all of the general ones speak for themselves. The difference between the 2 run speeds is that one increases your mount and one increases your base run speed, they don't pile up.
Scout
Again most of them speak for themselves. Additional mitigation to your defensive buffs (ie Weapon Elusion if I'm not mistaken), and skill bonus of offensive songs (ie Weapon Boon). End line is a nice detaunt. It is advisable that Strengthened Links be taken by all bards, unless the only thing you ever do is raid in a dps group, not ever in OT or MT grp or never solo/group
Bard
Skill bonuses of defensive songs (ie Weapon Elusion), run speed increase, damage increase and an extra proc. The end of line is all crit multipliers go up by 10% (ie from 1.3 to 1.4). Defensive Ballad is another good ability in here for the skill bonus increase on parry buff. Treat this like you would strengthened links
Dirge
Improving damage/debuff of rhyming curse, a nice little damage reduction, base heal increase on our heal spell (with stifle removed with 5 AA), damage + heal + casting speed increase to Howl of Death, duration + damage increase to Vile Blade, additional DA to fortissimo, a big passive disease based buff and a big DA increase to anyone of your group members but you.
Known Useful Configs:
Bard
Thanks to Singinbasher of Oasis
AGI 4-1
STA 4-4-4-8
WIS 4-4-6-8-2 (or 4-6-4-8-2 alternate)
INT 4-4-4-8
AGI line for bump to do both your stealth attacks. STA for 10 double attack for your group(ups your dps quite a bit as well). WIS for DKTM and Allegro. INT for +DPS mod and +pierce/slash/crush(primarily for tanks as most everyone else is capped).
AGI 4-4-4-8
STA 4-4-4-8
WIS 4-4-6-8-2
INT 4-1 or STR 4-1
This spec adds poisons, loses +dps mod and +pierce/slash/crush. INT is for Rhythm blade to get initial bonus to +pierce/slash/crush. STR is for Turnstrike so that you don't have to joust on area of effects. This is for a raider who's group is capped on those skills/dps mod.
STR 4-*-*-*-2 (up to preference-i.e. waisted points)
STA 4-4-4-8
WIS 4-4-6-8-2 (or 4-6-4-8-2 alternate)
The dreaded bladedance spec. You sacrifice some of your groups/personal dps for AE immunity. If your raid can do without this spec at all, I recommend doing so. The Swashbuckler AE blocker is on a fast timer and is common spec(EoF tree). The druid AE blocker is on the fastest timer(2 mins), but stuns them and has very short range. It does not require as many waisted points as our spec.
Dirge
Just decide what your play style is. Most dirges get the 5 sec CoB increase, a lot have a spec that inceases all their debuffs, quite a few put just enough in to get the 20% proc chance, while others want magnetic note, a few have a solo spec with points into extra healing on Howl of Death and Siphon Blade. Just play around and see what spec you prefer.
Shadows
Shadows is very debatable atm. Personally, I have 2 specs...Damage with support OR flexy support. Flexy support involves all the bladedance crap and any buff increases i could lay my hands on, wheras my main AA config is a bit more thought out. In shadows:
Primary AA Spec:
General - 00055000, just health and mount increase. Subject to change for anyone, a lot of people choose deity pet and suchlike. Choose it based upon what you want...as it doesn't really matter.
Scout - 0055000, just damage increase and reuse time...so that I can use sinister strike more often and my crit amage is higher on quick strike line.
I don't have the detaunt because I rarely need it, having the dark elf detaunt.
Bard - 0550551, damage increases etc. I have deaths edge but again it's totally up to you what you have, but at the end of the day, dexterous sonata is a must have.
Dirge - 00500511, as I do a lot of duo with a SK, I like personally to be able to heal him and then continuing attacking with spells. If you never need to use your heal, then place them in deathly howl/viral infection/defensive curse.
My Flexy Support Spec (NOT RECCOMMENDED)...
Like I said, it's just for when I'm needed to be all around support, no dps whatsoever (or very little). I have Bladedance spec, degradations/luck/life and death, and anything that improves buffs in my shadows line (and Health/Power increase on general). This really is spacker spec and I wouldn't reccommend it for general usage, but I keep it for when I need the other abilities I wouldn't normally have.