For the astronomy job seeker, I would HIGHLY recommend an NRC postpoc. The trick with these is that (1) they are frequently not posted in the AAS Job Register and (2) you basically have to have somebody on the inside helping you. NRs are available at all NASA centers and most other government labs. Contact people at the center to get a book on NRC opportunties at the center(s) where you want to work. Then call people who are listed in the book til you find a compatable match. If you get this far, your chances of actually getting the job are better than 1 in 10, which is a lot better than most of the stuff in the job register. The forms are a pain, and it takes a while to get an answer, so start early, and remember that applications can be submitted quarterly, so you don't just have 1 shot per year.