Links
Below are a selection of sites which I have found repeatedly useful in the past, and I which I hope will remain so for the future:
Wikipedia is a fascinating resource. Although entries can be inaccurate and subjective, it still holds value.
ABEbooks seems to be one of the better sites to find antiquarian volumes.
Steve White's site, Online Archaeology, is making a great job of evolving a general portal for the discipline of archaeology, abstract from any specific period of history or pre-history.