Early 2013 Google announced they are partnering with fonts.com by offering their complete collection of open source Google Fonts available for free for download to your desktop.
To this point Google Fonts have mostly been for use on the web, typically used by web designers to incorporate any of the nearly 500 Google Fonts in their web work (if you count italic/bold etc. there are over 1,100 fonts).
By having Google Fonts available on your desktop/laptop, graphic designers can now use any of the Google Fonts fonts in their work.
There have been ways to download zip files of Google Fonts, but up to this point it was a fairly difficult process, and there was no way to sync any updates to Google Fonts or newly added fonts to the Google Fonts library, so the process is getting much easier for those who would like to store fonts locally for design work.
Another nice benefit of having Google Fonts locally on your computer is that web pages using Google Fonts will load faster (if they are using the fonts you have downloaded).
Google Fonts are managed on your desktop via the SkyFonts application from Monotype (free download for PC and Mac).