The article How To Download The Entire Google Fonts Catalog from The Next Web details an amazingly simple way to add over 1,100 totally free fonts from Google Fonts (who knew?), using the SkyFonts service/app from Monontype.
Once the service is installed on your Mac or PC, you can add any of the Google Fonts here at will, and they are instantly available (at least they were in Pages on my Mac) to use! It could not be more easy!
Also, in case you didn’t know, you can add any of these same fonts to be used within Google Docs/Drive. When editing a document, click on the Fonts drop-down menu (between the paragraph style (probably ‘Normal text’) and the font size drop-down). At the bottom of the Fonts menu, you’ll see an option to ‘Add fonts…’ I’m not sure how many you can have available, but the selection is incredible.