Right now? Nokia N900, without a doubt. Maemo is a lightly hacked Debian, the official toolchain is gcc-arm (admittedly without autoconf, but that's a blessi

Right now? Nokia N900, without a doubt. Maemo is a lightly hacked Debian, the official toolchain is gcc-arm (admittedly without autoconf, but that's a blessing if you're in control of your own source), and deployment is straight-up apt. Plus it's a decent Python dev platform if your tendencies veer in that direction. If the "lightly hacked" part gets in the way, you can even debootstrap a real Debian release onto the device and develop in that. The hardware is decent as well; it certainly feels more solid than the HTC slide phones I've played with recently, and despite dropping it a few times it's barely got the shine worn off after 8 months. All that being said, it's entirely unclear what the future of the platform is; Meego could sink without a trace in 6 months, and I don't know if Nokia are planning a successor device. In my mind they'd be insane not to, but sanity hasn't been Nokia's hallmark of late.