Well,
AIM = BeeJive, this was introduced in a thread previous to this one. And it is very kickass. I highly recommend it.
Office = Google Docs is quite easy to use on a touch. Powerpoint is lacking.
Firefox = Safari...what is wrong with Safari? It is a nice web browser for what it is worth...and why would a "webapp" be Firefox? It is an application that browses the web, but to Apple that isn't a "Webapp"..a webapp is an application that is exclusively only capable of being used through Safari.
Personally, I would love to see:
Wikipedia -- A NICE wikipedia based webapp that is very similar to the website's look and feel. It isn't bad to just go to the website directly, but it does take a while to load.
eBay -- made by eBay, so also very similar. With a category browse and full search and nice color support and fast bidding support.
Campusfood -- Haha, this is totally a collegeboy's request...but it would be sweet
NationalCity banking -- Again, kinda a small clientele, but my bank would really make me happy by putting out one of these
TV Guide -- So I know what's on on my way home.