To gain some insight into how people use one of my sites, I've hacked together a script that sorts web log entries into groups of "sessions", where a session is a time-bounded set of accesses from a given IP/host. This scheme works O.K., except for a handful of visitors who come in via AOL (and hence AOL's proxies). I can disambiguate a single user by lopping the proxy name off of the hostname, but that doesn't fly when sessions overlap. I've tried using the User-Agent to keep users sorted out, but that's not 100% reliable.
Much of the contact is static, so I can't rely on tracking via session cookie. (The site is hosted at an ISP, so I can't install mod_usertrack.)
How have other people dealt with this kind of after-the-fact tracking? Any pointers will be appreciated.