there a lot of sites abt PIC programming
piclist , are some of them
there is not much difference b/n the normal and A version . pls refer the datasheets .
Just a later silicon revision, but you really shouldn't be considering the long obselete 16F84, it was replaced by the cheaper, higher spec, 16F628, which is now the 16F628A, last century.
The PIC16F84A can use crystals up to 20 MHz, resulting in double the execution speed.
I’m not sure whether PIC16F84 is available now. Its better migrating to PIC16F628A or PIC 16F88 version which has advanced options as earlier mentioned.