At Bar Ferdinand, check out the "Dia de Valentino" $30 prix fixe brunch or the $65 & $75 prix fixe dinner menu. The offerings are posted on their website.
Darling's Diner will be selling heart-shaped cheesecakes in personal or full sizes. Try the Belgian Chocolate Mousse variety if you really want to woo somebody. They'll also host a Lovers Brunch and Lovers Dinner.
What happens when over 100 Philadelphia artists decide to celebrate Valentine's Day? The Group Heart Show at Jinxed/Toothless Cat Gallery in the Piazza on February 13. If you're the card-buying type, there's no shame in choosing one here, because there will be custom Valentines from each artist. Check out the list at Jinxed Philadelphia.