This is by no means an extensive list. Others exist, but even a few of them together will provide you with meaningful intelligence.
Here they are:
Gives you stats on websites, including global rank, country rank, number of sites linking in, and good basic audience data, including demographics.
Like a lot of services, Amplicate operates a “fermium” model. A quick search, which will give you a “hate” vs. “love” snapshot for a brand, is free. Pay $19 and you get a year’s worth of data. And for $199 you can download various industry reports.
Amplicate also has a blog with useful information. For example, apparently half of online chatter about Foursquare in 2011 was negative.
Board Reader will search for mentions across forums (including sites like Quora) and will also churn out a chart based on mentions over time.