Odyssey Space Research
From SpaceWiki
Houston-based Odyssey Space Research has quite an impressive resume, having worked for NASA, ESA, and JAXA (the Japanese space agency), as well as SpaceX and Orbital Sciences on the NewSpace side of things. Judging by their Projects page, their big things are Guidance, Navigation, and Control (GN&C), simulations, and general "analysis" (a.k.a. the category where they put all the miscellaneous research).
Odyssey also sponsors the SEDS SpaceVision conference, presumably so they can troll the crowds of attending students for good space-research job candidates.