I ran across this "tool" a year ago or so, figured it'd be useful to post here and maybe a suggestion for JP for the tools and toys section?

www.netcraft.com/whats

You go to this site, enter the site you want to know about and it'll let you know what apps and os the server of the site....

www.antionline.com -----> Apache/1.3.22 on WINDOWS 2000
www.bonfire.tk ----------> Apache/1.3.22 (Unix) mod_perl/1.26 on Linux
www.goddessunleashed.tk ---> Same as bonfire.tk

It seems everyone with a .tk domain is running on Linux (Yahoo Geocities...)