BAStats Pre-Release - very nicely done. It provides direct insight into referrers, page views, etc. on a web server. Simple time-based filtering and fairly straightforward filters. I have no idea how it processes the data itself - whether there are appropriate data cleanup runs included, since it's still a pre-release. But it's quite nice to sit in front of the website and get live views. And much more manageable than a tail -f on the access log.
One effect of BAStats is that visitors receive a cookie. Anyone who rejects it, no problem - everything works as before. The cookie simply serves to identify a visit.