One not that useful but I found it myself this week:

When typing on the "email address" keyboard (the one with the big @ and period buttons in alpha mode) you can hold the period and get .net, .com, etc. (Too bad most apps that ask for an email address seem to forget to use this special keyboard!) I knew lots of touch-and-hold typing shortcuts, but that one was new to me.

And one I just saw at Engadget (in an article suggesting that Palm may hold the patent on this):

In your Contacts List, you can just type initials to pull someone up in a search. Use a space in between. So, to find John Smith, you could type J-space-S. That's actually kind of useful! I'll search more and scroll less now.

STROGG: Change We Can Believe In