Besides the obvious of email, sms, and phone calls; I use it for work(IT) twitter, AIM, internet on the go, tech blogs, music...Pretty much everything.
Twitter, great time killer. I'm also trying to get back into facebook since everyone I actually know (you know in real life) is on there. Most of the people I follow Twitter are friends from this forum.
internet first. then emails. then calender. after that it gets fuzzy cause there are a few games I like to play and a book reader that I love! I am reading 2000 leagues under the sea when I have spare minutes
I spend most of my time on apps...specifically Twitter, Facebook, Myspace and the weather and a few games such as SolFree.
The other percentage of my time is texting and phone use. I also have MobileMe and utilize the calendar as well. I also take a surprising amount of pictures with my phone.
I have music on it but rarely use the iPod feature.
Listen/watch music/videos/podcasts every morning and evening on my 1 hour train ride to and from work. Otherwise I use the phone and email majority of the time. I use almost all aspects of the phone but just on a small scale, other than changing my backgrounds daily.