I once had this challenge on how to convert a .dat file on a VCD to mpeg. After scouring the web, I stumbled upon VCDGear which has a GUI version built for Windows and a Console version for Linux.
Unfortunately, its not at the repositories but its easy to install. Simply download the file from this page and then double click on the deb file and easy does it.
Execute it by typing vcdgear at the terminal and you'll see the options and command syntax to follow. For more info, visit http://vcdgear.com.
Another app I love is WinFF. I first saw it at PCLOS repos but its not included at the Ubuntu repos. Simply download the deb file from here and double click on it to install.
WinFF is a cross platform batch GUI for FFMPEG. It will convert most any video file that FFmpeg will convert. WinFF does multiple files in multiple formats at one time. You can for example convert mpeg's, flv's, and mov's, all into avi's all at once.
Great for converting flv's downloaded from Youtube to 3gp's to be uploaded to cellphones. :)
For more info, visit http://biggmatt.com/winff/.