As you may know, they're not there. Yet.
Now, various people are tossing around ideas for 4e bards as an arcane leader type and will probably eventually write up the sort of drum-pounding buffbot that the class has been slowly morphing towards.
However, the new focus of 4e on combat stunts/powers means that it's entirely possible for someone to create the sort of charming rogue I'd like a bard to be. I'm not going to try and seriously craft a custom class at the moment because I don't want to worry about getting the math right to be sure the class is fairly balanced.
My bard is a cheerleader/buffer to an extent, but also a trickster. Not well suited to doing direct damage, but great for screwing up the enemy's attacks and setting them up for someone else to hit them.
Some possible powers:
Good Timing (class feature)
If an enemy misses a bard on an attack and there is another enemy adjacent to that enemy or the bard, the attack must be rolled against that target (possibly at a penalty). So if you swing and the bard ducks, you may hit someone else.
Quick Step (at-will)
Bard slides to any unoccupied square adjacent to the target and rolls (Dex or Cha? vs Will). On a success, the enemy is Dazed until the bard's next turn.
(Picture a halfling darting between an ogre's legs, and the ogre turning around in confusion trying to reorient.)
Circle Dance (encounter)
Bard rearranges the positions of all characters within (close burst 2?). Enemies resist on Charisma vs Reflex. Characters can only be moved to open squares, you can't use this to put someone over a cliff or into a fire, but you can set them up so that someone else can knock them in.
(With fancy footwork and dodging, the bard leads everyone around in a circle and they all end up somewhere else)
Uplifting Song (encounter)
All allies within burst 5 may spend a Healing Surge and add the bard's Charisma bonus + 1/2 level to the HP regained.
(A stirring anthem to recharge a flagging spirit!)
Bang the Drum (daily)
Choose a target (range 5). All allies adjacent to that target make a basic melee attack against it.
Anyway, these are just some ideas... if I were better at this sort of tactical combat I'm sure I'd have more. The point is that none of these actually allow the bard to attack, and yet they're all quite useful...
UPDATE: Apparently bards are due out in the upcoming PHB2, aimed at March 2009