No it doesn't.
From the SRD:
Aid another [Standard][AoO: No]
Description: If a character threatens an opponent with whom an ally is engaged in melee combat, the character can attempt to aid the ally as a standard action. The character makes an attack roll against AC 10. If the character succeeds, the character's ally gains either a +2 circumstance bonus to attack that opponent or a +2 circumstance bonus to AC against that opponent (the character's choice).
Emphasis mine.
It's a circumstance bonus. And as we all know, with rare exceptions, multiple bonuses of the same type do not stack. Therefore it doesn't stack. You can have one person aid another for the attack bonus while another aids for the AC - that works fine. But by the way this is written, you can't get multiple attack bonuses. I understand this is changing in 3.5 but the question was in 3.0