Platforms: iOS, Android, Windows 8 (all free)
This app offers more reason to kill the fax machine. Back in the days before storage giants like Google Drive and Dropbox, or using email attachments, YouSendIt was the go-to tool for sharing large documents with other people. It's very handy for one-off sharing of big files, especially with someone who's not yet hip to other cloud services. You can stash 2GB of files on its servers and get 50GB of transfers for free, or pay $14.99/month for additional storage and security.