Here is a two freeware program that I like to use cause they are easy to use and free ;-)
They are pretty helpful for those who don't have softwares like Photoshop etch.
The firt one support many file formats so you can open a variety of file and save them after as jpeg file for photo uploads (internet photo sharing). You can also take screen capture shot for those who work with word processor as Ms-word files etc. and then save the captured screen as a jpeg image.
http://www.irfanview.com/
The second one, is mainly for screen capturing and saving to different graphic format including jpeg as well.
http://www.techsmith.com/products/snagit/default.asp
Below is an exemple of a screen capture done with snagit.
