The guys at MikroElektronika have done it again!
Here is another brilliant new development board for the PIC32: the Mini-32
This board makes a PIC32MX5 fit in the exact form factor of a standard PIC16 or PIC18 40-pin DIP with full pin-out compatibility (with approximately 80 PIC models), but it operates at about 10 to 40 times the speed.
Of course you get 64K (+12K) of FLash memory and 16K of RAM too. A CAN interface complements a number of serial ports and the USB port is already there for you to bootload new code into it without having to use any additional hw development tool.
At USD 25 a piece, it looks ideal for breadboard-ing and quick (classroom) experimentation.