Two sites I know of are:
If the upcoming occasion necessitates an evening out at a restaurant, why not purchase a gift certificate for half price. Or, you might find a store listed where you enjoy shopping.
Furthermore, if you frequent money-saving blogs, you might find a promotional code saving you even more off your purchase. Also check Retail-Me-Not for promotional codes before you buy anything on-line, yes, that's including half-off depot and restaurants.com--savings on top of savings.
As always, be sure to read the details before you make your purchase. For example, a restaurant may be offering a gift certificate for 50% off, but might require a minimum purchase, and gratuity and alcohol are usually omitted. Remember it's only a good deal if it's the right deal for you or someone you're buying it for.
One great option for sale now at Half-off Depot is a gift card for Earth to Old City. You pay only $12.50 for a $25 gift card. Since I've already been there many times, I know it's a great place to buy gifts, so I've purchased one gift card that I'll post on my bulletin board at home. Next time I'm in a pinch for a gift for someone's new baby, wedding, or another special occasion, I can just grab the card and go shopping!
I also purchased a card for The Glowing Body, as I intend to write a review in an upcoming blog after I eat at their vegetarian cafe.
So, if you have an anniversary coming up and a restaurant you like is on the list, now you can save half off your dinner by ordering your certificate in advance!