http://www.freeimages.co.uk/
This site has a much smaller range to choose from than some bigger stock photo sites, but the images are royalty-free and you don't have to pay to use them.
http://www.stockvault.net/
Stockvault looks like a good image resource, with a range of categories, some nice and polished looking images, and most of it is free of charge.
I love this site! It has all sorts of quirky video & film clips that are free to use. It's an archive of "ephemeral" (advertising, educational, industrial, and amateur) films. Most of them are black and white. There are some great ones, like a series of 1940s clips on how to teach your children good manners.