IIS logs and TFS
A caution - you probably want to turn off the IIS logging on your TFS services if it happens to be on. Our server has all the data on the D drive, so the C drive is rather small. It causes some problems when the 5 gigs of logs for access to the version control service maxes out the available drive space. Our 20 person team was generating around 100MB of logs every day. (I could tell when people worked the weekends, too, because the build server's periodic pings only account for about 500K per day, so I could see activity levels as a graph of log size )