I got a link to this from the Forensics mailing list from SecurityFocus.
It seems to be a free service to analyse new viruses and spyware. You submit the suspected file to the sandbox and they will perform an analysis of it and send you the results. They will obviously produce a new signature for their products from this also.
I've not tried it, I don't come across new spyware/virus, but it might be a useful service to some.