I came across the stock.xchng site the other day. It looks as though it could be a useful source for free pictures. We used a couple in an animation project. The generous photographers are offering their pictures free and there is a good selection. We seemed to get several good pictures from all the searches that we did. Certainly worth a look.
The free site is promoted in a bid to take you on to their stockxpert site which has royalty free but paid for pictures. This sister site has many more pictures being uploaded and has a 50/50 revenue sharing scheme for the photographers. You pay more for higher resolution pictures but only up to a $10 maximum, so it seems good value.
Perhaps we could put some of ours up there. See what the return is. Which reminds me, all those slides need to be scanned in!