There is a new feature in Apple's beta of iChat AV that allows you to change your photo quickly. By clicking on your picture in the buddy list, you can quickly select a new image. By clicking the Edit Picture button, you can even use a digital camera to take a new Photo. Images are added by simply dragging your image file onto the screen. The bounding box can be set to the area of the photo you wish to use as well as the box can be graded to select a specific area. When moving the scaling slider, depending on the size of the image either the bounding box or the scale of the image will adjust.
[robg adds: And if you haven't tried this yet, the nicest touch is that you now get a 16 picture "history," allowing you to quickly and easily change your image as your moods swing!]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20030630233812237