We've featured a number of file-sharing services, but you may not want to host your files on a central server. Free web service iSender will instantaneously transfer a file directly from you to a friend, no server or software required.
The process iSenr uses isn't so different from direct file transfers in AIM or other similar IM protocols, though it's quite a bit more reliable. All you do is visit the site, pick the file on your computer that you want to share, and give your friend a private link to download that file. Instead of uploading the file to the server, iSendr will wait for your friend to click the link and transfer the file directly to them.
It's pretty handy if you'd rather not have your files sitting on a server for all to access (even if the link is private), or if you don't want a file to take up space on your server while you wait for your friend to go download it. And, since iSendr never uploads the file, once your friend clicks the private link, that link cannot be used again (so even if someone did get a hold of it they wouldn't be able to download the file). It even encrypts the information and allows you to password protect the link for extra security. Hit the link to check it out.