Tony,
If you want a Twitter client for your Q, try CETwit:
http://rainmakerrc.googlepages.com/ceTwitsp_11.CAB
If will allow you to do just about everything you would do on your Twitter page.
But, if you're like me, and just want at quick way to post (which is part of the appeal of using Twitter and other similar services on a cell phone) and not necessarily to read other ppl's tweets, then SMS is probably the way to go. I personally use the mobile version of HelloTxt's website (m.hellotxt.com) on IE because it loads fast and allows for simultaneous posts to Twitter and other sites (like Facebook, Jaiku, MySpace, etc.).