talk to a mcu ? from where? from PC?
if your want to talk to mcu from PC you should really think about "finding PC with serial port is very hard now days" so a mcu with USB support should be a good choice... in the 8bit PIC range a 18F4550 (or 18F2550 is his smaller brother) is one with a lot of sample code you can learn from, and on the 16bit PIC you have PIC24FJ64GB002 that is my favorite .. (comes in trough hole 28pin package) ... The PIC24FJ64GB002 comes with not as much examples as 18F4550 but it is great chip, not too expensive, easy to work with ...