For those teams that don’t have access to Photoshop, GIMP is a great open source program alternative.
Here are some tutorials to get you started.
I haven’t tried GIMP before, but I do use http://www.picnik.com/ for most of my simple photo editing needs.
I’ve used GIMP before (mostly because it comes prepackaged with Ubuntu) and while it’s very nice for some things, I had trouble completing some tasks that are extremely simple in Photoshop (Even just trying to import two images, crop/splice them together, and save it was a challenge).
Also, for those who prefer to use vector graphics (In my opinion they are far simper to work with for most graphic design applications) but can’t afford Adobe Illustrator, I recommend taking Inkscape for a spin.
http://inkscape.org/
And even if you’ve never used vector graphics before, give it a try, it’s extremely easy once you first get the hang of it!
GIMP is a great program, but if you plan on using it for the first time, allow yourself extra time to get used to everything. I’ve used the program for several school projects with good results. And, it’s free (always a plus!).