As for the search engines themselves, look them over and develop a couple of favorites. Metacrawler is one of a number of a number of meta-search engines, that is, it conducts searches on a number of search engines simultaneously. Speaking of directories, one of the best is Librarians Index to the Internet a well maintained index from the California State Library. Its one of the first places to go to. Direct Search out of GWU is a very fine directory of databases, focused on scholarly issues.
Libraries are always good places to go.
In particular, look at the Marine Corps University library but remember that lots of other military educational institutions have them. For maps, check out West Point's military history department's Map Collection as well as the maps at the Perry Castaneda Library , a very large collection at the University of Texas. The DOD Dictionary of Military Terms is a bit slow, but a handy reference. The British MOD Links to ministries of defense around the world, as well as some non-governmental international and lots of British sites. The US Army's Foreign Military Studies Office has an excellent and enormous list of links.