I have been surprised by the amount of keyboard shortcuts that make everyday use a lot easier on the 8900. Sometimes it helps to look at the manual (I rarely do...).

Here is my list of the ones I now use everyday:

alt-shift-delete = reboot
R = refresh page (in browser)
U = don't show browser status bar (in browser)
K = open bookmarks (in browser)
space = open phone log
two times space (quickly) = enters a point and space ". " in text
enter = use instead of trackball click

You've seen the homescreen shortcuts?

Look here Home Screen Shortcuts - BlackBerryFAQ

Although those are for the 83xx model, 99% of them work on the 8900. I know the R for Alarm does not.