I have tons of stuff to do at home today but I was thinking of taking the BART tour of its new lines to the San Francisco Airport: "Saturday, June 21 from approximately 3 p.m. to 8 p.m., BART will be offering free rides on its new San Francisco Airport line. Riders wishing to tour the new line and its facilities will be able to ride free between the new South San Francisco Station and Millbrae Station, or into the BART Airport Station, making all station stops."