1. Cook your Valentine's favorite meal for them. Make sure to set the mood with some relaxing music and candles from the thrift shop. Regardless of what you cook, it will be cheaper than buying it at a restaurant and you won't have to wait in line. Dessert is a must! A great and inexpensive dessert that is romantic is fondue. You can melt chocolate over the stove or look for a fondue maker at that same thrift store (I see them at Goodwill all of the time.) Here is a link to some great recipe ideas: http://www.food.com/recipes/romantic
2. Go to the thrift store (MAKE SURE TO READ FURTHER!!!). Have a game in which you each get a set dollar amount to spend on the other person like $5 or $10. You then can spend that much money on gifts for your Valentine right then and there. This is great because it gives you the opportunity to be goofy or sweet.
3. Make coupons for your Valentine that are acts of service. If you're a married couple you can get really creative with this (wink wink). For everyone else some great ideas would be a back rub, foot rub, cleaning a room of the house for them, washing and vacuuming their car, doing their taxes, or anything else they may like. They can expire after February 14th or be valid forever! You can find love coupons here http://freebies.about.com/od/valentines-day-freebies/tp/printable-love-coupons.htm