This list of 5 7 Browser Based P2P File Sharing Services is very cool. This type of service works by using Flash to connect two computers together remotely via an encrypted URL.
How does it work? First the file sender selects the file on their hard disk, and receives a special URL which they send to the proposed recipient. The recipient clicks the link and the file transfer starts automatically in the browser. It’s all done directly from one hard disk to the other via the web browser, which of course means it’s cross platform too.
The only caveat? Speed. if you want to transfer large files using this method and you’re not on a super fast connection, you’re going to be taking a looong time for the transfer. Which is a pain. But for small files over fast connections, it’s very cool. Oh and of course, both parties need to be present for the file transfer to happen, so no overnight ‘fire and forget’ transfers as with Yousendit type services.
Update: Two more services from the comments makes 7: