The Battletech universe has over 1000 years of future history, over 30 years of real-world history, and a whole lot of games. It seems like each new game in the setting sparks new discussion of the old ones and the setting in general, so here is a thread where maybe we can keep that kind of thing going all in one place.
Links and resources:
Classic Battletech (board/minis/tabletop RPG) official site, introduction to the universe (with downloadable quick-start rules and setting primer in PDF)
Mechwarrior Online: official site, GWJ thread
Harebrained Schemes' upcoming tactical game for PC :official site, GWJ thread
Mechcommander 1 and 2 and Mechwarrior 4:Mercenaries have been available as free downloads in the past, but the download sites I have for them are defunct.
Running MW2 under DOSBox (GWJ thread)
This is just scratching the surface -- please share links!