At Wigflip.com a few very nice online programs are available to add more fun to your pictures. This is a great thing about the Ä°nternet: not having to install a lot of software on your PC to do nice things.
Check out their website and other online programs here.

If you like a lot more options and great ease of use, check out Comic Life - OK, you need to install this on a Mac, but it is certainly worth it!