Under Linux, use xvidcap and either host the results if you have the
means or use Google video (much better quality than YouTube).
Or what I used was "recordmydesktop", available for gentoo and debian
for sure. Produces nice theora (ogg) output. Link:
http://recordmydesktop.iovar.org/about.php
The lowest barrier to entry may actually be Jing: http://www.jingproject.com/
It handles the capture, the transfer and the hosting.
http://popey.com/Creating_Screencasts . Whilst recording to OGG format is great, there's precious little tools around to re-encode to other formats from OGG as the source. It's also not sensible to try to transcode for a lossy format to another lossy format.