I am thinking of starting a website, but for it to work, I need a ruby script constantly running in the background. Can you recommend any web hosts that allow this?Thanks!
Web hosting that allows background processes?
web development;web hosting
If you have VPS or dedicated hosting then you can set up cronjob for this.  Heroku lets you run cron job as addon HostingRails allows it.   EngineYard allows it too   I'm sure most others will do.