Look at one of the Cygnal Development kits at this web page.

http://www.cygnal.com/support/developmenttools.htm

They range in price from $99 US to $149.

The kit for the C8051F020 is a great value. It is here:

http://www.cygnal.com/Products/C8051F020DK.htm

....and you can look at my project web page here on 8052.com for discussion on using the development kit for the C8051F124 here....

http://www.8052.com/users/mkaras/CygnalEval.phtml

Michael Karas