ScummVM is the ultimate retro adventure gaming tool. Things are really that simple. It's an excellent piece of software that easily, freely and intuitively let's you play the vast majority of classic graphic adventures, by supporting all Lucasarts releases (from Maniac Mansion and Monkey Island all the way to Full Throttle and The Dig), most Sierra games and a huge variety of offerings by other major developers; it even supports quite a few modern, indie AGS-crafted releases.
Happily, you can now enjoy the retro brilliance of ScummVM on your Android phone. It costs absolutely nothing, played everything I tried on it perfectly and can be downloaded from the Android Market.