Whew, RubyForge got 209K hits on Sep 21. It seems to be averaging about 160K hits per day during the week and about 100K per day on the weekend. And that's just the GForge part of the site - that doesn't include all the project web sites or the RubyGem downloads.
The machine's load average is still pretty low; it's about .10 to .30 most of the time. There are still some things we could do to tweak performance, too - we don't even have a PHP cache thingy like PHP Accelerator installed yet. So we've still got some headroom.
Another option would be to get some more RAM. We've got 2 GB in there now and I think that it can handle 16 GB. We could probably keep the entire PostgreSQL database in memory - it's only 650 MB on disk.