Today on Groupon, get half-off a visit to the San Francisco Musuem of Modern Art. Entrance is just $9 instead of $18. The catch is you have to use the ticket between 8/27/10 and 9/3/10. You can buy 2 tickets with this deal.
Also offered today, half-off indoor go kart racing in Rohnert Park. You can get 2 8-lap kid races for $15 or 2 14-lap adult races for $23. Use the same Groupon link as above.