These are some resources I've found useful in my
research. Thus, for example, I have a link for Madison County, NY
research (where I had lots of ancestors) but none for Genessee County
(where I had none that I know of). Follow some of the "General links"
below for more comprehensive lists of sites.
I find this site ugly, poorly organized, and way too heavy on
the self-congratulatory award graphics. But it may have its
uses and so I'll keep it listed here anyway. Links to "over
70,000" sites.
Using either of the above outside the USA is just a headache.
Multimap provides nice-looking street-level maps of the UK, and
larger-scale maps of the rest of the world. I like it a little
better than
Streetmap
for UK street maps.