We all know that stock photos can be expensive, but at the same time well worth the purchase if it helps you get that final result you have been looking for, Check out these free to use stock images before you make that purchase at istockphoto.

www.freestockimages.co.uk - Great stock images for free!
www.openphoto.net - Nice easy to use and search open source and CC photos.
www.freephotosbank.com - Nice site 100% free.
www.imageafter.com - Mostly free or cheap, good for textures.
www.sxc.hu - Great free site.

www.mediawiki.or - Wiki for media files, photos, vector images, video and audio.

Other notable free, mixed license or very cheap stock sites.
www.everystockphoto.com - Good selection of free and very very cheap images.