Xcor Aerospace is a company founded by Jeff Greason. This company has been around since 1998 using research and development to determine all challenges to creating a fully reusable launch system to get payloads into sub-orbit. Their motto has been to focus on solving all the prolbems for a resuable vehicle. They started their early develobment with a small rocket engine with only 15 lbs of thrust. From this small beginning they have worked their way up to building a rocket powered plane named the X-Racer. In this development process they have claimed the title of most liquid fueled rocket firings in the world and over doubling NASA in a distant second place. They have also developed piston pumps for rocket fuel and a light weight fireproof material for constructing fuel and LOX tanks. They are currently in the design and construction of their suborbital vehicle named Lynx. Greason recently mentioned Xcor would further research into a 2 stage orbital rocket where the second stage would be able return to it's point of origin (presumably with wings).
Xcor has some strengths and weaknesses in their company that I would like to point out. Xcor's main strength is rocket engines. They have consistently produced lighter weight easier maintence rocket engines through a method of under promising and over delivering. They started small and consistenly created larger systems and have worked with a variety of different fuels. I think it is fair to say that this company knows more about rocket engine design for small to medium rockets than any other company to date. This company has been working mainly off of R&D contracts to fund their development and progress. They havent run into any serious funding problems as of yet but that might have to do with their track record of consistently putting out results. Xcor's current biggest weakness is that they know very little of aerospace design from the ground up. Their previous vehicles were modified kit planes. I think this will cause their development of the sub-orbital space plane to take an extended length of time. Smartly Jeff Greason has not put any kind of time-line on their development and flight testing. If all else fails for the company the will still be the leading manufacturer of rocket engines.