If you don't need the convenience of FLASH In-System-Programming, a ex-Tandy friend of mine has a company at:

http://www.axman.com/

While that compny is Motorola-centric now, they still have some 8051 evaluation boards that they're selling.

80CXX Microprocessor Development Boards and Systems
CME-0552 Single Board Computer $130
CME-0562 Single Board Computer $115
http://www.axman.com/Pages/order.html

Remember that you must have an EPROM burner and eraser to program these boards. That can cost you the difference if you don't have one around.

-Jay C. Box