Official Site: Yvonne Craig has her own excellent official site, with information on her career, images, merchandise, and more!
Batman Series: From the maker of Yvonne Craig's official site comes batfriend.com. It's a feast for the eyes with superlative graphics from the Batman TV series, including fun stuff for Batgirl fans. It also has a lot of historical information, and the maker's exploits as a fan.
Batman Series: Another great fan site for the Batman TV series is The 1966 Batman TV Tribute Site. It not only has information on and images of Yvonne Craig as Batgirl, but tons of other great stuff about the Batman series.
Star Trek Series: Curtis Fox's Star Trek - The Original Series - Web Page has grown significantly, including its page dedicated to Yvonne. This contains the largest selection of images of Yvonne on the web (including but not limited to the extensive collection of Reag's Archives), and a short interview Fox conducted with Yvonne concerning her role as Marta in the Trek episode "Whom Gods Destroy."
Elvis Movies: Yvonne has not only worked with Adam West and William Shatner, but she was also once the King's leading lady. Elvis' Women is a cool page about the leading ladies in Elvis' movies.
Video and Images: Luis' Yvonne Craig Page has a large and excellent collection of images, video, and sound clips.
twof has made a page dedicated to scenes in the Batman TV series where Batgirl is subjected to terrible traps. Batgirl Bat-Trap contains images, video, and information, and includes the Siamese Human Knot.
The Batgirl Webring, a link exchange for Batgirl web sites, some of which include Yvonne as Batgirl.
Jonathan Sanders' Dark Knight Damsel page has images of Yvonne Craig as Batgirl, and a nice collection of information on Batgirl.
startrek.com has a page about Craig's Star Trek episode, "Whom Gods Destroy," which includes a movie clip.
The Celebrity Cafe has an interview with Yvonne.
The Female Celebrity Smoking List states that Craig once smoked, and has accumulated evidence.
Trivia tribute has some images of Yvonne.
My Presley Gallery has some images of Yvonne from Kissin' Cousins.