The Success line of Aid Another reads:
The target gains a +2 bonus to the next check using the same skill or ability before the end of the assisting creature’s next turn.
Since you must use the same skill check as the person you're aiding, could someone else use Aid Another to assist your Aid Another check? Are there any rules that support or forbid this?
Some may find this useful when there's more than 5 in the group, since the Aid Another benefits are limited to 4 aides. This way, with stackable Aid Anothers, the extra individuals can have a hand in boosting the success of the direct aides.