TextMate is an excellent text editor for the Apple Mac. It's ideally suited to the agile web developer, and is very easy to extend with your scripting language of choice. It became famous in the Ruby community, and is (credit where it's due) the only reason that I switched from Linux to Macs several years ago.
TextMate is by no means the only editor worth investigating; I'm also a bit of a fan of Emacs, having used it for 10 years before I got TextMate. It's just not as pretty, or as easy to customise (but PeepCode can help you with that). Before Emacs, I used vi, and these days spend most of my time in Vim and Tmux.
TextMate 1 was a commercial product. TextMate 2 has been released as open source, and is being moved forward pretty rapidly by the community.
How often do you find yourself wanting to check the source code of a locally installed Ruby gem? Do you find it painful digging around your filesystem to locate the gems directory? With
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