AVerMedia AVerTVHD Volar (A868R)
It is supported under Linux since kernel 2.6.27 
This device supports ATSC (i.e. OTA Digital TV) only. A pig-tail (included) connects the device's mini-RF connector to standard coax cable.
From lsusb: ID 07ca:a868 AVerMedia Technologies, Inc. Tested device was in a opaque metallic black case. AVerMedia's website shows a unit with a translucent blue case that may differ.
Making it work
Using a kernel > 2.6.27, required modules are:
No firmware is needed, the EZUSB chip appears to load via I2C from an EEPROM. Device must be connected to a USB 2.0 port to function.
(As of Dec 2008) This device seems to be universally on clearance and/or significantly marked down on both auction and common retailer's sites. Perhaps discontinued?