I've written a free tool called Botspotter to track search engine visitors. Identifies those that appear to by browser based too, like Slurp. Check out http://bots.pcpropertymanager.com/ I'd be keen on feedback. It's in its early days, but hey, it's free!
Looks pretty nice... I'm assuming it's some sort of include within your webpages? I think spidertrax did something similar, but definitely does not have the reporting capabilities yours does. - Shawn