Photoshop

Gimp

Getpaint
http://www.getpaint.net/

Tools to resize crop add special effects

http://www.picresize.com/
Resize, shrink, and crop your pictures online for free at PicResize.com. Resize photos before posting them on Facebook, Twitter, Pinterest, Reddit, Tumblr,

Picassa

Flickr has editing features through an integratedwebsite which I think is called Piknik.