Just dropping a line to anyone interested in Battletech/Mechwarrior. Microsoft gave MekTek Studios to go-ahead to release Mechwarrior 4: Mercenaries for free, along with the two expansion packs. MekTek has already added an impressive amount of content to the game, which they are also offering for download. Total count of assets is somewhere around 100+ 'Mechs, 100+ weapons, and 50+ maps, all for free.
The popularity of the free release crashed their servers, but when they come back up, you can get more info and find the download here: http://www.mektek.net/projects/mw4/