The two are quite often related. For example, some people believe that the giza complex (they generally either don't realize or ignore the fact that there are many other buildings around the pyramids and sphinx) was built by survivors from a previous civilization (which is believe to be where the story of ATlantis came from). Supposedly, the three large pyramids mirror Orion's belt and the Sphinx aligns with the constellation Leo in 10,500 BC. Supposedly, this is signifgant of an important time to 'Atlanteans'. Supposedly, these Atlanteans 'nurtured' what we today believe is the earliest civilization. There are also the obvious theories of alien construction, which I think is a cop out. Theres a lot of misinformation and crap, but kernel's of truth are there, I think. For example, it's become more widely accepted that the Sphinx may be much, much older than we now thing. As well, it is become more accepted that perhaps the pyramid of Khufu, was not originally the pyramid of Khufu.
However, I think one of the best (though I personally would find it the most fascinating the the Flem-ath theory of Antarctica was true, but I think the findings might point to other htings) theories for 'Atlantis' IF it is anything more than a social commentary, is Bolivia.
Then you have the 'Emerald tablets of Thoth' which are of arguable authenticity, which point to a chamber under the Sphinx's left paw, same as Edgar Cayce 'prophecied'. Japanese studies show that there MAY be a cavity under the Sphinx, while other studies supposedly show huge caverns that house a city.
There are stories of sonic frequencies that open doors in the great pyramid, and lead to a giant underground city, unfortunately, the film was confiscated. Yeah...
Atlantis
http://flem-ath.com/
http://www.geocities.com/webatlantis/
Giza
http://www.angelfire.com/wy/1000/Giza.html (nutter link)
http://www.crystalinks.com/sphinxfacts.html
http://www.abovetopsecret.com/forum is an amazing website, because there are a fairly even number of both pro and con posters for all conspiracies. Links to all sorts of new Giza and Atlantis theories can be found in the Ancient Civilizations forum, as well as information on the dubious, but fascinating Bosnian Pyramid.
Enjoy!
Epstein didn't kill himself.