I've got a pantload of links on my machine at work. Bump this to the top on Monday morning to remind me - virtual desktop seems to be 'effed up or I shut down the machine when I left today.
Google earth is very good, but it requires a software download.
USGS Mapstore lets you download pdfs of 7.5 minute (and other) topo quads.
The feds run a site that is pretty good, but the name of the administrating Department escape me...