I blogged steampunk miscellenia last term for a Victorian Literature course, here.
Update: An excellent article, interview, & overview online here.
Steampunk fiction features a heady blend of influences like Jules Verne, H.G. Wells, and inventor-hero fiction from the American pulps of the 1800s. It typically includes some mix or mash-up of airships, mad (or, at least, heavily-invested) scientists, eccentric inventors, Victorian-era adventure, and clockwork technology of the sort that we've largely abandoned. Its godfather may well be Michael Moorcock, with his novel The Warlord of the Air, and it gained huge popularity in its first wave because of novels like William Gibson and Bruce Sterling's The Difference Engine in the 1980s and early 1990s. Other classics include Paul Di Filippo's The Steampunk Trilogy, K.W. Jeter's Infernal Devices, and Tim Powers' The Anubis Gates.