To find out what visitors to your site are up to, you can either do it yourself with log analysers or save yourself the trouble and outsource the analysis problem. The pros and cons of each approach are complex enough that neither solution is the best in general - it all depends on the site and how it is used.
But should you conclude that outsourcing is the way to go, check out SuperStats from MyComputer.com (http://www.mycomputer.com).
The service provides, as the feature list indicates, death by reports. These can slice and dice the data to an insane degree and even allows you to export to Excel and comma-separated values files for you to do your data abusing.
SuperStats comes in two flavors: Enterprise and Small Business Solution, targeted at high and low volume sites, respectively.
In fact, within the Small Business Solution there are several graduations of traffic level that attract different pricing schemes.
The base monthly pricing for SuperStats Standard is $9.95 per month for up to 25,000 page views with an extra 50 cents for every additional 1000 page views per month. For $99.95 per month you get up to 50,000 page views with additional monthly traffic fees for 50,000-plus pages views per month.