Sources

If you don't take your own photos you'll have to find the sources somewhere else. When you look for an image to distort you'll need large and sharp sources. Google image search can be useful, but there is the copyright issue and often a quality issue. I'd like to recommend istockphoto.com for cheap, but good sources (the used to be gold fish is from istockphoto). You can download a lowres image for 1 dollar and highres from 3-5 dollars at istockphoto.

And when we are on the subject I'd like to recommend the Adobe exchange community for inspiration, templates, scripts and image solutions.

Other good image sites are:
gettyimages (requires a bigger budget)
stock.xchng (used to be free, but still cheap)
mayang's free textures (thousands of large quality textures)

Google image search can still be inspirings and as you know can search for images on the major search engines like yahoo, altavista and msn.