I hadn't realize just how much data was being served up by the RubyForge mirrors. But Dennis Oelkers, who runs the main mirror master, pointed me to a status page - and his mirror alone is serving 20 GB per day of RubyForge HTTP traffic! This works out to an average bandwidth usage of 230 KB/sec. That's a lot more than the DSL line that RubyForge is hosted on could have handled, especially along with 7K email messages per day, Subversion and CVS traffic, and so on. So, in summary, thanks very much to the RubyForge mirror providers!
In other news, a plan is in the works to get RubyForge moved into a colo facility. This should give us more bandwidth and a more reliable infrastructure, and should also lower the temperature in Rich's basement by several degrees. Thanks to Ruby Central for their efforts on this!