How about using the ones from shredder.com? They have new ones every day and they allow you to link them to your web page for free as far as I can see. They might be a nice addition to have on our opening page here at RHP or just have them elsewhere. Here's the link:
They aren't usually "find mate in x moves" type puzzles, but are just "find the best move" types. Some are just finding a single move, and some are a series or two or three moves. If you go to their site you can check them out and see what you think!
Another option would be to see if some of our own members can put together a variety of chess puzzles that could be used for this purpose. Most of us probably aren't that clever, but I'm sure there are a few around here who could do it. The posers and puzzles forum will have some at times, but not on a regular basis.