I started developing on linux, and it's really carried over to my mac, so I use the Terminal command line frequently and never really use xcode.

I strongly recommend homebrew [1], it's great for installing stuff, and I've never had a problem with it.

Another neat tool is Dash [2], which is a documentation searcher/viewer. If you like that kind of thing, it's great.

One thing I bought which was really useful was Witch [3], which brings back a more traditional alt-tab (command-tab) menu, where you can switch between windows instead of applications. It also lets you quit selected applications from the command-tab menu, among other things. Worth getting.

Another little app I sometimes use it Go2Shell [4] to open a terminal window in the current directory from finder. And you can use the built in `open` command to do the reverse. `open` is quite useful, so you can use whatever default application to open a file from the command line.

Another neat tool is `pmset noidle` (power manager set no idle), which stops your computer from sleeping or dimming the screen. Saves you from this situation (http://xkcd.com/196/)

[1]: http://mxcl.github.com/homebrew/

[2]: http://kapeli.com/dash/

[3]: http://manytricks.com/witch/

[4]: http://itunes.apple.com/us/app/go2shell/id445770608?mt=12