I've been reading about the DIY tablet projects out there (Carbon Tablet), and looking at some of the fun adult level "building block" project technologies (Arduino).
Whats really fun looking is the ARM based Arduino project that is pin compatible and uses the standard Arduino "shields". I've got an idea for an ARM based project using the 4.3in PSP LCD and Touchscreen shield, with gps, wifi, SSD card reader, IR, and accellerometers as a test bed. What would be hot would be to have a cool Open Source ARM OS.
Another idea is to build up an ATOM based Arduino project, use an embedded linux.
What would be nice is an unlocked 3G dongle.
Yes, I know, I'm asking for a better crunchpad, but since that one failed hopelessly, it'd be fun to design something that is accessible, with real open specs and readily purchaseable off the shelf parts so anyone could build a tablet.
No, it won't be cheaper, but you will get the features you want.