If you're doing any work creating UI mockups, chances are you've downloaded a few Google fonts to your computer. Doing this manually is tedious, and you wouldn't be up to date when the fonts get updated.
SkyFonts is a free font syncing service that puts webfonts into your computer. It works with paid services like fonts.com, but also offers unlimited support for Google Fonts.
This by far is the most convenient way to get Google Fonts onto your computer. Adding new fonts is mostly a one-click affair, fonts updates are automatically pushed to your computer, and you can even conveniently install the top 50 Google Fonts.
Monotype Skyfonts is available via Caskroom as