Alison Raab Labonte
Alice, this is a great list of semantic search engines! I use quite a few of them, especially Exalead. I would also add http://www.allplus.com to your list -- it groups items by keywords (which it extracts on the fly) along the left-hand side, to allow you to drill down a little more deeply into the precise item you are seeking. It seems to be having some difficulties gaining a toehold in the search market -- I hope it sticks it out. I'd also second Peggy Garvin's advocacy of USASearch.gov and DTIC.
I'd like to turn the discussion a little and point out that it's probable you are all using your libraries (they just might be known as "knowledge centers" or "information research centers"). You're just doing it virtually. A major reason for that is the digital transition of much useful content, thus the dwindling need for a large library to house books. The materials often still need to be purchased (publishers of valuable information still seem to want to be paid) and managed -- all behind the scenes. Thus, it seems you "never use a library anymore." For example, most libraries have Google Scholar "hooked up" to their subscription research resources so you'll get to full-text. To take another example, you might be finding via Google or other search engines reports from respected institutions such as EIU, OECD, or IEEE, but your access is gotten for you by your library, which negotiates prices on your behalf and purchases relevant materials for your institution. Finally, I'd like to say that if you are not talking with your resident librarian (or "information specialist" or whatever s/he is called), you probably should. They can let you know about the "gray zone" of information that is not indexed on the web, but HAS to be purchased in some form for you to get access to -- a prime example is Jane's, which has invaluable and expensive content not readily or thoroughly available on any semantic search engine precisely because the publisher does its darnedest to make you pay for its content.