She created the webcomic Smithson, with art by Robert Stevenson, Brian Moore, and Roger Langridge. The strip was first called More Fun and premiered in September 2003 as one of the original strips on the subscription-based site Graphic Smash. The strip, which makes some use of infinite canvas techniques, follows the exploits of the self-appointed campus superhero, Chamucka Man, and several students who attend Smithson College.

In 2005, More Fun moved to Webcomics Nation under the new name Smithson. It is currently suspended.She works for Viz Media as an editor and volunteers at the Cartoon Art Museum. She has also written for Marvel Comics, including their 2005-2007 Marvel Holiday Specials.

In 2005, Garrity won the Outstanding Writing award, and was also nominated for Outstanding Comedic Comic, from the Web Cartoonist's Choice Awards, She was also named co-Lulu of the Year by the Friends of Lulu, sharing the award with the Flight anthology.

Garrity lives in Berkeley, California, with her husband, artist and Cartoon Art Museum curator Andrew Farago. Garrity has contributed to the magazine Otaku USA and reviewed manga for Jason Thompson's The Complete Guide.