You'll notice that there's a new bright and shiny button on the IM window toolbar (the white square with the swanky green arrow). We've tried to make the whole transfer process as easy as we could, so all you have to do is click a button and upload a file. The receiver on the other end will get a link to click on (similar to a meebo rooms invite) and all they have to do is click and accept. We're only allowing meebo account holders to send files, but anyone can receive... even your friends who are not on meebo (but should be =p). We're not quite supporting this feature in Safari yet, but hopefully soon!