Shamrocks Solitaire is a fun pile based card game that is one of my personal favorites. One of the things I like about it is that almost every hand dealt can be won, but it does require a lot of thinking before you make your moves. There is one major constraint placed on pile building, and that is you can't have more than 3 cards on any pile. Aside from this, building is pretty flexable because you can build the pile up or down, without worrying about the suit. You start out with a lot of piles, but you have to be careful because once you remove all the cards from a pile, that pile is gone for the rest of the game. Because of this you want to be really careful before you take that bottom card off the pile.
Like in most solitaire card games, your goal is to build up the 4 suit piles from Ace to King by suit.