I figure for a small email, you could probably use the screen.

Anything beyond that and you'll have to find a way to graft on a keyboard. Usb or bluetooth ?

For real coding I'd do it with a cross development kit, which is how most phone software development is done.

Android supports bluetooth keyboards and mice. I've tried it with my Archos 5 device... it's quite usable for web browsing.

it'd be cool if you could keep the keyboard physically attached, maybe with a hinge mechanism of sorts.