My first thought was a 4square like site with "geeky categories" for check-ins. You get more points the geekier your check-in is. A large national museum gets you some points, a local museum gets you more. Same with big city vs small rural book stores or comic shops.

Tech stores get you a few points, locally ran places, the type with computers lying open everywhere get you more.

Also worth points, corporate headquarters, conventions, and libraries.

Or, go deeper. Do this with a browser plug-in, and count websites people visit, and length of time spent there. Yes, game analytics. Sell the data anonymously. Spending time reading Wikipedia is one thing, spending it logged into GitHub is another. Rack up geek points for the above mentioned categories too.

I like it, but my first concern with this would be privacy.

On the other hand, something like this seems to exist already: http://social.wakoopa.com/

A travel deals site for people wanting to tour silicon valley historical sites? hook it up with tours of companies hq's combined with lecture series and exclusive resort packages.

I like this idea. Maybe even things like Jonothan Coulton's cruises and conventions. A full fledged travel agent for the like minded. Or hire one and you just do the site and take a cut. Also have a kids section where you list youth tech summer camps or space camps, etc. The premier geek getaway site.

"The path of the True Geek" comes to mind. You can be serious or tongue in cheek, your choice (though my spiritual views and my sense of humor are intimately intertwined).

Healthy trail mix delivery service for geeks to keep them energized for late night coding sessions.

I want to see the street view of all the geekiest places on the planet in one place.

I think this is what you're looking for: http://www.geek-maps.com/

tours for startups/founders