Hello.
You can find a good examples on Brinkster PHP Ming site: http://www.gazbming.com/ there are free code samples of sokoban and invaders games. On http://todbot.com/ming/ you can find also a ming-pong game for Perl wrapper. Rewriting them into Ruby should be not as much difficult. Certainly Ming can be an option, but FlashDevelop + FlexSDK from Adobe are very well suited for writing games. It is up to you, the matter of choice. Pawel