Like Aisu, my tablet is the Ultimate Communicator.
Add to his list Mauku for Twitter / Jaikus and X-Chat for IRC, and a couple of good choices for RSS readers for keeping up on other things like blogs / flickr / etc.

mClock for a bedside clock when travelling, and of course Numpty Physics and Liqbase for goofing around.

VNC viewer makes a great remote control, by the way. It's a very easy install on people's computers, and it really impresses people when you can flip through pictures on a computer slideshow being shown on TV... from your tablet while sitting on the couch.

Like debernardis, I use OpenOffice as a great on-the-road Office suite.

But mainly I love just hacking around... "Hmm, can I do that, I wonder?"