One way to have frugal dating night is to use gift certificates from Restaurants.com. I have tried them in the past and they have worked, plus it's a great way to try new restuarants that you normally wouldn't go to or wouldn't know about. I will say though, that there aren't many restaurants available in some areas (including mine), so I'm sorry if you can't find anything.
Additionally - READ THE FINE PRINT before buying the gift certificate. They don't work like a normal gift card, but more like a 50% off coupon. Check the details about gratuity or what you have to spend prior to getting the discount. Make sure it's worth your while!!
Currently the $25 gift certificate is only $2 when you use the code INDULDGE when checking out. The offer expires 1/19/10.
Let us know where you go!! Post a review of your restaurant!