Over the years I have used everything from Doteasy to $50/month managed hosting. Places mentioned above like Site 5 and are bad news unless you're running a tiny website, as they cram 200 to 400 sites onto each server, and don't really offer any performance guarantee. On top of that the business model for big shared hosting companies like site5 and Doteasy is to raise your account level and charges every time you exceed their limits. Additionally, these places are renowned for their lousy service, as this is part of how they make money: cram as many sites on a server as possible, with as much automated support as possible and as little real live people support as possible.
That said, the best I have found in response to the above general situation with web hosting comes from two places:
This is good for just setting up a site on the spur of the moment. One account lets you set up as amny domains as you like. Domains are billed by bandwidth and storage. Freeduino.org lives there, and costs about $1.50 a month. This is sort of programmer's heaven for web hosting, as you can get into the nuts and bolts of the site config very easily, or set up hosting and SQL for for a new site literally in minutes. it would be the perfect host if they had better uptime, which I would guess is between 98-99.5% a month. Not a good place for Arduino.cc, but worth mentioning in general.
http://www.fusednetwork.com
This place is simply unbelievable. They have shared or dedicated hosting, and I think it is possible to get something in between, i.e the service is scaleable, both up and down, by request. Their support is the same as I used to get with managed hosting- i.e. your emails go to the network admin's Blackberry. You always get a response within the hour, often within minutes. Uptime ratio is something like 99.99%. Speed is excellent, as is the service. If you put arduino.cc here, you will not be disappointed.
D