Steam is updating their regular hardware survey this evening.  Once you quit whatever Steam game you're playing, you'll be prompted to answer a couple of questions & upload your hardware load-out to their servers.  The results of the survey can be seen here.   Interesting that the percentage of systems with 2GB of RAM has outgrown that of the systems with 512MB.  Also interesting (at the time of this writing) is that the number of systems with nVidia video cards simply dominates the ATi camp by 20%.  Realtek AC97 still owns the audio chipsets, though.  Good to know that some things don't change easily ;)