I currently use HostGator and they are pretty affordable and I get good speed/uptime with them on a shared hosting plan. My board isn't that large so I can't comment on how it holds up with tons of activity.
But here is the reason why I love HostGator.
1 click downloads for backups! And an easy upload feature to restore from a backup! They do autobackups on Sundays but it's nice to go in every few days and download a backup yourself. I just login to the control panel and click backup. Not sure if this is common with a lot of other hosts, but this is a really cool feature for people running a message board.
I am on the baby croc plan. I don't work for them and as you notice the link is not a tagged link where I get credit. Just wanted to share the info on the cool feature.
http://hostgator.com/shared.shtml