Alexa can give you a traffic estimate for all sorts of web sites, big and small. When building reciprocal links, it's a perfect tool to sort out which sites are particularly important. Click next to the window, you're shown even more information in a drop down box. The site ownership data is expanded, to provide a street address and phone number, if listed. You're also shown how Alexa users have voted for the site, plus a Yahoo Internet Life review rating and a RSAC rating, if either is available.
Voting is somewhat helpful.
If you like a site, you vote for it. Alexa records the votes and shows them to all users. You can vote once per site. This doesn't seem to be the most popular feature, since most sites have only a small number of votes, either way. But as a general guide, it's interesting to see.