I use two; Bihira for my own site and small client sites, because it has everything I need, albeit somewhat small storage space, and is dirt cheap at $2.50 a month on the cheapest plan. They were recommended by a friend in web dev.
I use TMDHosting for my forum. When I was looking for hosting for the site originally they really stood out as having everything I needed at a good price point, and their customer service is just amazing. I have had a pretty major issue with them where they split my site between two servers during a cleanup of their servers, and half of my members could only see posts before the move while the other half could only see posts after the move, but they ironed it out extremely quickly once I figured out that it was in fact their fault and not something I did. I haven’t had any problems whatsoever since then.
I think, though, that my next large site will be hosted with HostGator. I’ve heard nothing but good about them, and their pricing seems reasonable. Media Temple sounds great too, but the price is a bit high unless you have a multitude of small sites or one big successful site.