Pando works a lot like yousendit and rapidshare except you download a client side app to run it from your machine. Pando is also offered as a plugin to many different IM's so I don't think it would be that hard to implement into VB. They also have guides and what not for server integration here:
http://developers.pando.com/ - you have to email them and get approved for the server integration manuals.
This would be a great plugin to send big files straight to VB. It could be available right next to the upload attachments function.
This would just serve as a great way to upload big attachments to VB as the current attachment upload tool lacks a progress bar among other things. You could also possibly upload directly to VB without even being on the site...