Yesterday I wrote about my screencast production adventures. For a screencast demo I was working on I explored all the FLOSS screencasting tools I could find including RecordMyDesktop, and Istanbul. They all suck by varying degrees but xvidcap, though it doesn't look like much, definitely sucked the least.
If the binary package for your distribution crashes and burns try building xvidcap from the sources on Sourceforge (not the same as the *.orig tarball from the Ubuntu package for some reason). That usually produces something usable.