Plain text ebooks from the authors and publishers at Smashwords.  They lack much formatting, but they're readable on virtually anything.

	Gesture Recognition	by Xiaoyi Zhang July 14, 2010	Free!	174 words	Sample 50%
	Buggy's Adventures in Motoland - Buggy Discovers Motoland	by Kathleen Bosman July 17, 2011	$0.99	11204 words	Sample 20%
	Austin and the Deadly Scrapyard Crusher	by Stuart Taylor Nov. 25, 2011	$0.99	40408 words	Sample 10%