These days I never use Photoshop.
For webdesign and image editing purposes, I use several online applications.
Primarily I use Aviary tools. It provides variety of products like, Image editor, Vector editor, Effects editor etc.
Other vise I use Sumopaint. You can use Pixlr for simple picture edits and add some cool effects for your images.
Previously I use picnik. But they are closing.
If you are working on a heavy resolution file, then you can use Gimp, Inkscape kind of opensource softwares.