The official Garbage site is located at garbage.com, this links to the bands Tumblr account.

The guys mainly keep fans updated with news via their official Twitter account or via Facebook. Shirley does the majority of these communications.

Shirley has also been updating the fans via her official Facebook page as has Butch Vig from his Twitter profile.

All of these links are 100% confirmed as official Garbage channels.

Some additional sites you may like.
Smart Studios: The former official site for Smart Studios, the boys’ studio, where Garbage albums have been mainly recorded.

Spooner Fans: The official website of Butch and Duke’s old band, Spooner.