Previously leaked as the "Click", HTC's Tattoo has replaceable covers that you can also design yourself. It runs Android with HTC's Sense interface (like the Hero), and has a 2.8-inch resistive touchscreen (eek), 3.2-megapixel camera, MicroSD storage, and 3.5mm headphone-jack.
Update: Other key specs include 240x320 on screen resolution (QVGA), 512MB ROM, 256MB RAM, quad-band support, GPS, Bluetooth, Wi-Fi, FM Radio, Digital Compass and G-Sensor.
HTC plans for the Tattoo to reach Europe in October, and the rest of the world in the months after that. It's possible the Tattoo could be cheap enough to cost nothing with a carrier subsidy/smartphone plan.