Geeksphone, known for their open Android phones called “One” and “Zero”, is no more in the Android market, but have released the first two Firefox OS developer phones called "Keon" and "Peak". And: You can actually purchase them!

Both look nice, but aren't exactly high-end devices, in fact, with only 512 MB RAM (and as they are build with Qualcomm's SoCs, this means even less RAM for actual application) and thus not too interesting.