Well, luckily my most problematic forum stalkers live in out-of-the-way cities, so a quick view of a sock-puppet's IP location usually tells me who it is. I also just like to keep track of trouble makers using various metrics in case they develop into problems later.
If you ever have a moment, maybe posting a list of useful info gathering sites like that would be helpful. Maybe I'll add in my own and code them all into a crazy little "info overload" css-controlled popup div for admins who want to be able to dig up lots of info on troublemakers with the push of a button.