MKVToolnix is a set of tools to create, alter and inspect Matroska files under Linux, other Unices and Windows. They do for Matroska what the Ogmtools do for the OGM format and then some.
Since May 1st 2003, the Matroska libraries themselves and my Matroska tools are officially available. Although all of them are still under heavy development, I consider MKVToolnix to be stable. I urge you to download the software, use it and report any errors you encounter to me. I'm always grateful for good bug reports because I make mistakes and you guys normally find them. Your feedback is important to me :)