Also the Canon Rebel T1i has gotten a firmware update here. If your camera is reading 1.1.0 then you don't need the update, this can be found under the settings options...camera must be in a creative mode such as "M". The update focuses on the two following items, follow instructions on how to update (its very easy):
1. Enhances the reliability of Live View shooting 2. Fixes incorrect indications on the Arabic, English, and Swedish menu screens
Canon has released the much anticipated 2.0.3 firmware update for the Mark II, click here to get it. However they have had users experiencing issues and will come out with a new update soon. The link above will allow you to sign up your email address so you know when the update is out.
Along with these two major firmware updates you can update some of your software if you use them. Canon updated ZoomBrowser EX, Digital Photo Professional, EOS Utility, and Picture Style Editor. Check your operating system for the version numbers as them might not be the same.