MKVToolnix is a set of tools that will help you 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.
With these tools one can get information about (mkvinfo) Matroska files, extract tracks/data from (mkvextract) Matroska files and create (mkvmerge) Matroska files from other media files.
Matroska is a new multimedia file format aiming to become THE new container format for the future. You can find more information about it and its underlying technology, the Extensible Binary Meta Language (EBML), at http://www.matroska.org/