May be you can just get to know the function available in the 8051 microcontroller first,such as interrupt system, timer and etc. You may refer to the RAM diagram for 8051 as well to have a clearer understanding for the location of respectative function. So that you can know where to program to when come to software part.
Yes, this is a good site to learn more about 8051. Erm, just for your information, 8052 is the same family for 8051. Just that 8052 have greater RAM space and one more extra timer if I am not mistaken. Enjoy your learning in 8051.