Can anybody suggest a simple & cheap programmer circuit for 8051 so that experiments can be done while learning ?
NO, Nobody can. You can obtain circuits that can program some derivatives of the '51. Stretching a point it could be said that every derivative of the '51 program differently.

The simple easy way to go is to use ISP chips such as the Philips P89C51Rx2, 89C66x, the Atmel Rx2 series or Cygnal.

This will save you the frustration and agony of going therough the mental excersize "is it my program or is it my programmer".

Please, be good to yoursel, use ISP, forget about building a programmer.

Erik