I recommend the cross-platform Sublime Text editor. It's very similar to Textmate, providing basic features and syntax highlighting, while staying out of your way. With its plugins you can easily add additional features.
For an IDE suggestion, I'd vote for PyCharm once you're developing more complex stuff http://www.jetbrains.com/pycharm/. Most worthwhile $100 I've ever spent when I compare the number of hours I'm on it with its purchase cost.