In the past, we have suggested uploading to external sites and linking us the demos. We have decided that this is too unreliable and would like to put this method behind us.
Everyone can now attach demos as part of their posts. This is done by selecting the "Attachments and other options" link while you are creating your post. Once this opens, you will see an "Attach" sub-section where you can browse your local files and select up to 10 different files to upload. Of course if you have multiple demos of the same person, then zipping them together is the best way to go.
Using the forums attachment system is much more reliable for us as there are no external links that expire, these demos will stay attached on our forums indefinitely.