that's all great stuff, and i've poured over much of it (specific to MWO) for many months...of course i started playing TT BattleTech back in '86, so there are many, many resources out there, much of which has been available for years.
for those who are familiar with the old MechWarrior games, you might find this version a little more restrictve in some regards. the developers are literally following the timeline of the canon day-by-day
starting with daily new feeds last year in the year "3048". so right now in the game universe it is 30 May, 3049. the short of it is this:
the invasion of the Clans does not happen until next year (first wave was march-april 3050). this means there will be no Timber Wolf (Mad Cat), Nova, Dire Wolf, Summoner or any of the Clan mechs until then at the earliest
. right now there are only the mechs of the Inner Sphere (IS) available. 11 have been announced (12 at launch), with 3 mechs in each weight class...light, medium, heavy, and assault.
here is the current list-
of the links white bear was kind enough to provide, the most important ones are the following:
this is the main site, of course
this provides all the lore, history, and specs for every mech/vehicle/person in the BattleTech universe
MechWarrior Online Wiki | mwo game, mechwarrior online, mechwarrior faq, mech game
this wiki is specific to MWO, and is therefore more concise, but much less thorough
of course if you are just interested in piloting a giant robot and blowing stuff up, then most of this information won't matter much to you