One of my ongoing interests is NTP, the Network Time Protocol, the protocol used to set a computer's clock. It's one of the oldest protocols on the net and it's something of a miracle. A few 76 byte UDP packets is enough to set your clock to within 100ms of universal time.
Back in 1999 I did a class project surveying the NTP network. I was excited to find today that someone benefitted from my work, doing a new NTP survey in 2005. The results aren't too surprising. The number of visible NTP servers doubled in six years. Time serving has gotten more accurate and network delays are lower now. There are proportionately fewer stratum one clocks and they are about twice as busy. In general the good ol' NTP network is just getting better with age. It's comforting.
One big change since 1999 is that modern operating systems all come preconfigured with NTP clients. Macs, Windows, and Linux machines all set their clocks from the Internet out of the box. I contribute to this; I put my own server into the NTP pool used by lots of clients, particularly Linux machines. Unfortunately basic survey methodology can't really learn much about those clients. I'm starting to study the client population a bit with my pool server, some graphs are here. I'm seeing something like 30,000 to 100,000 different clients a day.