Transferring large files to a friend is rife with hassles — cruddy IM file protocols, email size restrictions, overactive firewalls, etc — xFiles turns the hassle of large file sharing into a simple two-click process.
Visit xFiles, click the Share File button and select your file. Copy the URL and share it with your friend. All they have to do is visit the URL and xFiles forms a HTTP file transfer tunnel from your machine to theirs. It's simple, as fast as your two connections will sustain and works wherever your friends can download regular files from the greater web.
If you're looking for more P2P features than xFiles provides, makes sure to check out previously reviewed Dushare for simple P2P with password protection and built-in chat. Have a favourite tool for transferring files when they're too big for email or your friend's firewall is blocking you? Let's hear about it in the comments.