What are some good go programs for the iPhone, both for playing and for learning/improving?
But the better option is that I was able to get GoGui working - I did have to manually build/compile it myself but there is a way to build it so that it creates a real OS X Application. It's quite good, you can set any board position and then tell a computer program to respond from that point.
EDIT: For the iPhone I like SmartGo Kifu for playing games. 'Tsumego Pro' and 'GoProblems' for puzzles (they're adaptive) and 'Go Books' by smartgo for ebooks.