BitLet is a handy service for downloading BitTorrent files without the client. Just copy and paste the URL of the torrent you'd like to get, and BitLet will fire up a Java-based downloader that lets you choose where on your machine you'd like to save the file. The whole experience requires no software besides your browser and the latest version of Java.
If you feel like sharing something to friends using BitTorrent, you can use BitLet to generate a link that will start up using the service. This means whoever gets it will be able to download the file without any need for a BitTorrent client, or instructions on what to do.
The only hitch? It's nowhere near as full-featured as even the most lightweight BitTorrent clients. There's no way to adjust things like ports, bandwidth allocation, and block lists. You also can't see whether or not you're seeding, and if so, how much you've contributed. That being said, the service is young, and a fantastic solution for grabbing small to medium-size BitTorrent files in schools, libraries, or other public computers.