Research tools:
1. Alexa, of course. This will give you Alexa's score of the site's popularity. Anything >100,000 is useless since the sample of traffic is too small to discern a proper placement.
2. Compete - also scores the site. Different algorithm, same idea.
3. Quantcast - another score, different algorithm.

Alexa and Domaintools.com will give you a geographic breakdown of the traffic sources to the domain, useful when looking for int'l bizdev.

Compete offers some keywords users use to find the site on search engines.

Quantcast tries to estimate #s on demographics of users (male, female, income, etc)

If you build a matrix of sites you are interested in and then figure out where you can target and be successful, you can turn the matrix into a sales dartboard.