We're currently switching hosts and searching the earth for the right Rails hosting company.  There are some good high dollar solutions if you have big funding, but for those rebels in the forest building cool rails apps, I'd love to hear about your experiences good and bad with hosting.  We also need to run Python and Wordpress (PHP), which we can do through another host if we find the right pure Rails host.

railsmachine   seems good for non trivial apps.   others like site5 offer much less expensive solutions for small sites.

railsmachine gets great reviews for vps.   give these guys a whirl, they are ultra responsive but i don't have any empircal evidence under belt.  blueboxgrid

for rails apps we decided to go with a multimachine VPS cluster instead of one big dedicated server.

http://www.slicehost.com

$20 per month for a VPS with one-click Ubuntu install. Use the deprecated gem to install a full rails stack without having to do more than entering 5 lines of code. Cool Wiki with everything you need to know about deploying a Rails app on Slicehost 

It's actually called deprec not deprecated. Here is the link http://www.deprec.org/

If nobody has mentioned Dreamhost, they offer Rails setups for cheap (like 7 or 8 bucks a month).

Nice I'm checking out the three of these right now....

I've been through so many rails hosts and I'm generally a novice with deployment plus I'm running a one man show I don't have time to become a sever guru. So I found effective customer service as essential as the the price.

OCS Solutions delivered this amazingly, they continue to impress me with their service. Tech Support replies quickly (around 30min for a low priortiy ticket) and always helpful. I had my app up in an hour after signing up. Beats every other host by at least a day through simplicity.

They can also handle scaling you app too.
 

I just sent a support ticket through Dreamhost's website and got an email response in less than 5 minutes. Seriously. And my follow up questions were again answered in less than 5 more minutes. You gotta love that: question-answer-question-answer ... bam, bam, bam!

And the best part is that my 1st YEAR of hosting cost me only $22 bucks since I used a promo code!

Just an FYI and in reference to Dreamhost's Rails support, check out their wiki page about the subject.
Bottom line, you better have your RoR shit together when moving a working Rails app over the Dreamhost (e.g.: not for beginners).

I find Dreamhost's tech support pretty brilliant too.  Their uptime isn't the greatest but it seems to be getting better.  And as you say, it's cheap, particularly if you can get a promo code.  I also love their Subversion on their control panel - saves me such a lot of hassle as I never remember Subversion commands!

Don't try running a rails app on Dreamhost. I did. It is just slow, awfully slow (and that's with only 1 visitor, myself, when I tested the site ^^). The Dreamhost support is the best support I ever saw, I still have my Dreamhost account and I think I will never cancel it Their blog alone is worth being a Dreamhost customer, these guys are crazy. But for Rails apps, don't go shared hosting. Even if it's a small app, you'll need a VPS at minimum. If you want to make a pretty static website like a blog, where content is only updated when you put something there from an admin interface, then it's okay as long as you cache the pages.

A small comparison: Loading a non-cached Mephisto (best Rails blog app atm) blog page on Dreamhost - 30 up to 60 seconds. On Slicehost: under a second.

Using Capistrano with Dreamhost to deploy a Rails app can be quite troublesome, I wrote a small tutorial how to do it (in german), so if anyone here needs help with it, maybe I can help.

I don't find Dreamhost that slow for Rails - as long as you follow the FAQ for getting fastcgi running.  My have an ozimodod tumblelog (and a typo blog which I admittedly don't use) running quite smoothly.  Maybe it's not as fast as VPS but if it's perfectly doable for a personal site.  Obviously if it were something more involved then I wouldn't consider it.

Like I said, if you use a pretty static website like a blog where everything is cached and doesn't have to be updated that often it is okay, although your admin interface will still be awfully slow

We've got a big machine (dedicated tons of memory lots of bandwidth) and are adding several more.  We're always looking for collaborators working on cool things , so email me 9 [at]fivenin.es, maybe we could find ways to help each other out.  We didn't have any luck on the really low cost setups trying to get something that would work for commercial apps.  I do think you can spend in the $79 a month range and up to $125 with a good VPS solution with someone who knows rails (I have a good referral here pricing wise), and then up from there with big iron db server and one or two inexpensive web servers.