YouSendIt is a file-sharing service. It allows receivers to get files by clicking standard URL links. Since YouSendIt stores files on its own servers, you have to upload what you want to share, but then you don't have to leave your PC on to allow people to pick it up. The hosted transfer model isn't as flexible as peer-to-peer sharing, but it is easier to use for both senders and receivers.
In addition to a free service, YouSentIt also offers three premium subscription plans for people who want to send larger files to more users. It also offers a branded file dropbox for businesses that want to create an easy way for clients to send large files.
Winner: YouSendIt (YouSendIt.com)