Profile Picture Genius is a free application to cutting and resizing pictures which you can then take as a custom profile avatar. These avatars can be published to any website or use in your favorite instant messenger, such as MySpace, MSN, Skype, Flickr, YouTube, Blogger, phpBB forums, vBulletin forums and many others.

Though you can already crop and resize images with any simple graphic editor, Profile Picture Genius makes it even easier as it already includes presets for the most common avatar sizes allowed in all those sites and apps, so that you don't need to be constantly counting pixels.