Linux driver for the Griffin Powermate

PowerMate uber-basic userspace tools
A rudimentary Python interface to the powermate
PowerMate patch against 2.4.21 --- adds support for newer hardware.
Related sites of interest:
Griffin product page
Groom Lake Labs userland utils and kernel patching HOWTO
Oliver M. Bolzer's Ruby userspace tools
Leigh L. Klotz Jr's userspace tools

You should be able to get up and running by applying the kernel patch above to a 2.4.21 kernel and recompiling. You'll need to configure your kernel with CONFIG_INPUT, CONFIG_INPUT_EVDEV, CONFIG_USB, CONFIG_USB_HID and CONFIG_USB_POWERMATE set. The patch adds support for Griffin's latest revision of the PowerMate hardware. The 2.4.21 kernel driver supports the older hardware revision without modification.

The driver exports a simple event interface; the tarball above contains a pair of demo apps, one for reading movement from the powermate, and one for configuring the LED in the base. Any software which understands the Linux event interface should be interoperable with the PowerMate -- unfortunately this interface is relatively new, but I'm sure apps will follow.

Dale Martin has written up some advice on making this all work which may be helpful to you.