Aside from XVidCap, I also looked at a couple of other screen capture programs for Ubuntu. These are Wink and Istanbul. They didn't make my cut, though.
I've used Wink before, and for my purposes then it was okay. Wink outputs the screen action to Flash, and that's great for embedding it directly into web pages. Prior to saving you can also edit the captured video frame by frame.
As far as formats, though, it's not very flexible. What if I wanted to save it into another file format? Furthermore, it's freeware and not Free Software, and so I'm a little leery of recommending it.
Istanbul is part of the official Ubuntu repository. It's a simple no-frills application that's invoked from the Ubuntu taskbar. Output file is Ogg Theora, a free video format in the Ogg family. Maybe not as popular as MPEG or Flash, but it's an accepted format on Google Video.
However, Istanbul was a great disappointment when I was running it on my underpowered Thinkpad. Screen capture was very choppy and it blanked to black several times. It was thoroughly unusable.
This article from Linux.com reviews the same two programs but comes out with significantly more glowing marks.