I'm trying to run a Ruby on Rails project (redmine) on a VPS. It's working, but it takes quite a bit of RAM. The rails application has very light usage compared to the rest of the VPS. I have lighttpd running on the server as well.
I'm new to Ruby and know there are several ways to launch a webapp in Ruby. I'm currently just using webrick (and am okay with launching it by hand). Is there another way to launch a webapp that is more memory efficient?
Rails really just takes a shitload of memory, it's a damned big app. One of the things you can do is try to get Ruby Enterprise Edition installed but if you're on a VPS there's probably not much chance of that. But perhaps the best option is to drop the app on heroku and not worry about it anymore. You'll have other difficulties like setting up email to contend with but otherwise Heroku is the best thing that ever happened to rails (I think at least. Maybe Merb though :P)
If you're new to Rails, configurations, and even Linux - your best bet is Apache/Nginx + Phusion Passenger + REE. If your VPS is something you control such as Slicehost, Webbynode, Linode, or similar - then that'll be the easier route.
Slicehost articles should help you out a lot by walking you through each step of configuring your VPS. And the steps even work on other VPS hosting companies, just match up the Linux distro.
If you're really green to RoR and setting up VPSes's-es (?) and unless you need more than a 512MB slice - I agree with Chuck, start with Heroku until you hit about 3-4 dynos. And since the Redmine demo is on Heroku - you know it works!