Booze Allen Hamilton, BAE, SAIC, CACI, L3, Raytheon, and a few other ones that I cannot remember the names at this time. There are plenty of companies as you can see. Booze Allen and BAE have the most jobs available for companies that have the best benefits. SAIC is everywhere, but their benefits do not compare to what the last two offer.
Also, there are government agencies (federal jobs) that have IAs. NGA is the biggest one. DIA would probably be the second. NASIC also has jobs, but they are usually more specialized, meaning you need more than the average IA certification.