Crosswords (or xwords, to use its Sourceforge project name) is a free, open source implementation of the rules of Scrabble™ for handhelds. It is currently shipping on Android, with older versions still available for PocketPC (including Smartphone) and PalmOS.

Some people call Crosswords "Words without Ads" :-)

Android	PalmOS	Windows Mobile

Crosswords formerly shipped on the Franklin eBookman, but that platform is no longer actively supported and is not described here.