I have about 20 domains hosted with Hostgator and their servers are pretty cool. Ticket and forum-based support is good. Only that you cannot take backups if u use over 50,000 inodes (important if u have 20+ domains).
I've been with HostGator for over 3 years and have been very happy with them and their support. You can find some coupons for your first month here!
HostGator overfills their server too much now these days but their support is great. BlueHost is very good, better than HostGator in my opinion. Sean