1. Fujitsu P50 2. Panasonic 3. Pioneer 4. NEC I believe does some nice 50" models too. 5. Depending if you *need* HD resolution or not, there is an ED (extended defintion) 46" plasma from BenQ that is getting very good notices, and that is relatively cheap.
(People may switch around Panasonic and Pioneer depending on taste - Panasonic for better black levels, Pioneer for punchier colors).
The Fuji is more expensive than you're looking for. You might find the Panasonic/Pioneer and other brands at closer to your price point.
Go to AVSforum's plasma/lcd forum for research on this.
Rich is right, check AVSforum. His list sounds pretty much right. Although, there is a new Samsung plasma that is getting some hype recently over at AVS.