I've been a fan of Nick Bantock's work since I found the Griffin and Sabine
For anybody interested in ancient languages, Lexicity is a pretty extensive collection of resources. Most interesting to me, of course, are Greek and Latin, but it has a long list of them, including Egyptian, Estruscan, Hittite, Mayan, Old Irish, Old Norse, Sumerian, and more.
I finally have ebooks of Latin dictionaries. Excellent.