Tiny Animals On Fingers - a photoset on Flickr. Flickr Photos On Demand with getFlickr. In case you don’t know it yet, Flickr is great.
It is a lot of fun to upload, tag and caption photos and it is really handy to get a vast network of contacts through it. Using Flickr photos outside of it is a bit of a problem though. There is a Flickr API, and you can get almost every page as an RSS feed, but in general it is a bit tricky to use Flickr photos inside your blog posts or web sites. You might not want to get into the whole API game or use a server side proxy script as you cannot retrieve RSS with Ajax because of the cross-domain security settings.
However, Flickr also provides an undocumented JSON output, that can be used to hack your own solutions in JavaScript without having to use a server side script.