Box.net does not give you the share link when using a free account. It generates the link, but you cannot share it easily, will not even copy & paste. You have to click "share", then send it to your email (or someone else's) before you get a link that you can actually copy & paste, and then post it in the forum. It does give you 5gb storageas a free member though.
It sounds like Dropbox is a lot easier.