In conjunction with 'My reading list' (which I'm thinking of revising), I've decided to share a few websites which I find handy for research purposes.
First, Rob Brautigam's Shroudeater. It is, without doubt, one of the best vampire resources on the 'net. However, if you're into fictional representations of the undead, you'll want to look elsewhere as it deals with 'the old traditional undead corpse of the European mainland.'
Next up's Melinda K. Hayes' Vampiri Europeana, or, a bibliography of non-English European resources on vampires in literature, folklore, and popular culture. An invaluable resource, its 'Chronological list of pre-20th century resources' has been incredibly helpful in tracking down obscure vampire works.
If you're a Dracula fan, you'll find Dracula's homepage by Elizabeth Miller, handy. I'm a big fan of her work. She's the president of the Transylvanian Society of Dracula, Canadian Chapter, which publishes the Journal of Dracula Studies. Members receive hardcopies of the journal, but the articles are available for download here.
In terms of accessing resources, the Internet archive's been great for finding obscure, out-of-print books. Among other things, I found a copy of Augustus JC Hare's The story of my life, vol. 4 (1900) through the site. Readers might recall that title's significance to the Croglin Grange vampire case, but few have actually read the original book. Thanks to the IA, you can!
Lastly, Google Books, has also been incredibly helpful. There are many regional versions, depending on which country you live. I use the Australian version (by default). Indeed, thanks to Google Books, I vindicated an author's use of the term nosferatu.
Those'll do for now. If you feel like I'm missing something, feel free to offer a suggestion for the list.