Beginner 8051 microcontroller kit recommendation?
I realize that you're looking for an 8051, but I think that's an antiquated choice. For an old, trusty tool, 8051's are great, but I'd strongly recommend against starting there. They're widely used in industry because they're incumbent, not because they're the best.

The easiest way to start is the Arduino-- it's cheap and easy to program. You can program it with a subset of C/C++, at least to start with.

If that seems not hardcore enough, and PICs are ruled out, I'd start with an MSP430 from Texas Instruments. Digikey has an eval board with two different MSP430s for $100. You also need a JTAG programmer. You can get the TI FET, but I've had success with the cheaper Softbaugh programmer.

(But if you really are dying for an 8051, I'd start with an Atmel chip and the Keil tools.)