Talking about Microchip PIC32 chipKIT boards are good targets to port. There are different boards both with 128k and 512k flash. Great advantage is that board layouts, connectors are mostly compatible to Arduino shields and there are cipKIt boards too. For details see:
http://chipkit.net/products/
They have an USB boot loader so you can easily download code with AVRDUDE or MPLAB, no need for dedicated programmer, so entry cost is low even for newcommers.
I have boards and planning to start porting, but I have limited time to play with. Any one is interested to join?
Béla
uPython for chipKIT boards (PIC32)
uPython for chipKIT boards (PIC32)
Tiny Core Linux (piCore) developer
HAM radio call: HA5DI (Béla)
HAM radio call: HA5DI (Béla)