I use http://www.handango.com
for most of my software- I used to buy so much that I'm in their discount club.
But the software that I currently have on mine includes: facade, battery pack pro, eWallet, mobipocket (free e-reader- mobipocket.com), keep track, listpro, newsbreak, notepad mobile, resco tools, resco photo viewer, resco explorer, the popcap games pack, cubis, marble worlds, brain challenge, slot car racer, smart 4lign (connect four), smart chess, smart checkers, smartello (othello), spb arkaball, and sodoku sensei. The only software I have that I don't really use is listpro and notepad mobile. Office came on the phone and has been invaluable- if yours doesn't come with it, I recommend that also, though if you can't get that Documents to Go is a good alternative. I used that before I had Office. I tried bankarama and liked it more than keep track- it came down to the fact that ilium gives a discount for purchasing all of their software, and it interfaces better with quicken. I received pocket informant for free, but I haven't even tried it- but I hear that it's good also.
I know that's a lot of software LOL. But really, what I use day to day is mobipocket, Office, newsbreak, eWallet, facade, keep track, and the resco pack of tools. I can't recommend the photo viewer and explorer enough- the one that comes with windows is pretty gimped.