[JAMF]

Use imageshack. It doesn't require a login. You can upload multiple images and choose between getting various URL's to the pictures, such as "direct" (for the large image) or "BB-code" (for the thumbnail).

I prefer using Paint.NET for image editing. You don't get as many options as GIMP or PhotoShop, but it's small, loads very fast compared to others and is less confusing.