PySol is God's own Solitaire program. It is written in python and runs on just about any platform. You can play over 200 (count 'em) variations of the single-player card game, including everyone's favourites Klondike, and FreeCell as well as the fiendish Gypsy (my favourite). Others include Aces Up, Baker's Game, Canfield, Forty Thieves, Golf, Pyramid, Scorpion, Spider, Yukon,...
There are plenty, OK?

PySol has lots of alternative cardsets, you can play background music if you want to. It's your basic nicely designed GUI program.

PySol is written by Markus Oberhumer and is distributed under the GNU GPL. You can download PySol from the website http://pysol.tsx.org.

Go get it!