Robert Smigel seems to have a decent fanbase. I'm sure it's just a matter of time before the Comedy Central
TV Funhouse series makes it's way to DVD, though it needs to include all of the SNL shorts to truly be "complete". If I'm not mistaken, "TV Funhouse" is still a feature of SNL.
That's My Bush was rumored last fall for the elections, but never surfaced. The best I could suggest is to check their site (Matt Stone/Trey Parker) regularly for release information. They've been updating pretty frequently now that the second half of South Park - Season 9 is in production.
http://www.southparkstudios.com