Since this info costs an arm and a leg, I’ve been looking for viable alternatives to Hitwise data. To date nothing comes close (for free) however I have noticed a great little section of alexa.com which gives you some breakdown of interesting domain info.
Not only can you download audience data which even comes accompanied by a ‘confidence’ metric (nice touch), but you can view clickstream for the site which shows you where people were before hitting the site and where they went after.
From all of this you can build up a pretty compelling customer profile and make some great assumptions on what communities have the potential to interact with your customers, how a site should be designed and the language used… the list goes on.
Have a play!