Hello
I've found an interesting web site with free games and demos for Nokia Serie 60
http://www.systemcap.com/StressedFactory/en/J2ME/stressedfactory-j2me-int.htm
You can download the jar file and send the game to the mobile device with infrared or bluetooth without any cost. Also it's possible to download directly through GPRS to the mobile phone.
Personally I have enjoyed with two puzzle-style games called ColorStress and Labyrinth.