There are a few out there ... I know one is Smart Search by smarterscripts.com ... thats one of the cheaper ones ... then there is hyperseek / jackhammer that engines like iqseek.com, sex.com, blowsearch.com are using and prices start at like $3,000 for that software ... check out IQSeek.Com ... (i have been talking alot about them) however they suprised me ... they were big a while back ... but had problems and now back online ... they made me happy in the past 30 days ... I know they have a good affiliate program?
you could use free analytics software like GoogleAnalytics (earlier Urchin).. But you need to get an invitation from google though. I think its data very relaible and very user-friendly. There another one called NetTracker.. bit expensive but very powerful. If you need to track only few , then best one is GoogleAnalytics.