ODROID-U is the Ultra-Compact and Ultra-low-cost platform with 1.4Ghz Quad-core CPU and 1Gbyte RAM.
As far as we know, this board is the world’s smallest and cost effective US$69 priced Quad-core ARM PC.
Board dimension is only 48x52mm (1.9x2.0inch approx). Look at the pictures to feel how compact it is.
It is only 60~70% of normal credit card size.
ODROID-U2 comes with more computing power by 1.7Ghz Quad-core CPU and 2Gbyte RAM.
Other specifications are identical to the ODROID-U. US$89
(sames as used in Samsung Galaxy S3 and Note)
ODROID-X, ODROID-Q | Hardkernel
they also sell 4", 7" and 10" development tablets
ODROID :: Hardkernel