If you need a professional application server, particularly for rails, I'm recommending Rimuhost these days.
Their VPS plans are a reasonable deal, but, as always, the support is what is always most important when choosing a host unless it's a super small static site, in which case the big guys like mediatemple, dreamhost, bluehost are fine. (Oh and check wordpress.com if you need a free site.)
Just now I've been getting really clear, friendly, (and super fast) support from Brandon at Rimuhost, and he showed me a great trick for removing a password from a ssl cert:
cd /usr/local/apache2/conf/ssl && mv sitename.com.key sitename.com.key.with_password openssl rsa -in sitename.com.key.with_password -out sitename.com.key
Previously one of their techs was chatting to me well into the evening about a SQL issue I was having, free of charge, after he got off of work, just cause he was cool. and I love their VPS control panel, which lets you reboot, power down, and upgrade your RAM/HDD on the fly.
If you need a development and production box, they will clone your production VPS (for free), in under an hour. Fastest demo box I've ever set up!