As for SDK, I'm using Qole's ( http://qole.org/files/ ) maemo-sdk-v1_2.img.ext2 (a bit updated of course) along with easy-chroot scripts (I basically copied the easy debian scripts and changed the stuff alongside with few other bits to allow concurrent easy-debian and easy-maemo-sdk running), so it is also doable if e.g. you don't want to "pollute" your N900 with development packages (could be good for beginner programmers unfamiliar with this stuff I guess - the easiest step-by-step instruction would be: download this compressed image, uncompress it, change the name to the easy debian's one and run the "debbie" command in terminal... when you finish, change the filename or delete it completely and restore the original easy-debian file to its former filename - ta-dah!).