i am a beginner in microcontroller ...i was using pic16f877 but i switch to pic 18f452 as it is as i think most famous one in pic18f family , there is a book available for it "embedded design with the pic18f452 microcontroller"
Half a year ago, I found the PIC18F458 to be the most powerful DIP part (in terms of speed, peripherals and memory), which I use for easier prototyping. Not too sure about now, but the new USB chips look interesting.