I don't know if there is any support for this already, I can't find anything. It would be really nice, especially for the very large VOD files, to support a way to resume interrupted downloads or only download corrupted parts of a download.
I downloaded a ~2gb file from 'My Files', and after it finished I checked the md5 sum and discovered it was not the same as what is listed in the my files section. In cases like this, the only real option is to download the whole file again (took >4 hours for me). A method to download only the corrupted parts would make it a lot faster and save the rifftrax servers some bandwidth.
One good method is zsync: http://zsync.moria.org.uk/
It creates a checksum file that sits on the server with the main file, and the client downloads this checksum file and uses it to find out what parts of its local copy are bad and then downloads only those parts. This is what some linux distros (like Ubuntu) use to provide their CD/DVD image files.
I'm not that familiar with any other solutions (parity files maybe?), but this kind of thing could be useful for people without the most reliable connections.