" I haven't decided on what chip I want to play around with, so if anyone could give me information about anything it would be fine. "

Instead of trying to get general information, why not select the Philips 89c51rd2 and go about reading all about it ? This chip has been discussed in detail and a wealth of information is available on programming the on-board flash. Download the AN461 document from Philips and the FlashMagic software ( it comes with a manual ) from www.esacademy.com which is used for the downloading of code.

I presume that you have reached this stage after you have become familiar with the basic 8051 architecture and its register structure. If not spend some ( or rather plenty ) time on the material given in the Tutorial link on this page. If you try to by pass this, then you WILL be quite frustrated at your own progress in Flash MCUs

Raghu