Blobby Volley 2 is a nice volley ball game in the spirit of clbuttic arcade volleyball. However, the default AIs are beatable by jumping in certain point, definitely too easy. Found some AIs over at esnips, and for convenience packaged them for maemo. .install file available as usual. Just install the package, start the game, go to options and select some AI.
Warning: these AIs aren't easy to beat.