I want to mention a couple small pieces of Mac software I use often, but think are very good: Dash and Pester.

I started using Dash a few months ago. It's mainly a documentation browser, making it easy to download copies of all kinds of developer documentation, including Drupal, WordPress, JavaScript, jQuery, PHP, Python, XSLT, CSS, HTML, and many more. Dash also automatically keeps everything you've downloaded up to date, which is a big win over the PHP function reference app I used (and enjoyed) for years. Dash can also maintain a library of code snippets, and assign them hotkeys along the lines of TextExpander or aText. It's free to download and use, and currently $8 to unlock the full version. It's not a complete substitute for the online documentation (for example, the WordPress documentation isn't a complete copy of the Codex), but it's very helpful, even if you don't use all of its features.

Pester is a timer app with a very minimal user interface, but it makes it really easy to set alarms. I call it up with LaunchBar, then type what I want to be reminded of, choosing either some number of minutes from now, or a particular time in the future. All of this can be done with the keyboard, and it's very fast after the first couple of times you do it. I can set alarms to remember to switch the laundry in 40 minutes, put the bread in the oven in 20 minutes, pick up a package in a couple of days, whatever. I gave the author a shout-out on Twitter, but I wanted to mention Pester again. It's really good.