junk in a box idea is great but my math teacher told us that we should all dump our girlfriends before valintines day but not on valentines day so we didn't have to waste money on her.
if you live in an urban or suburban area, i would suggest make her dinner(food network says chicks like that), than go for a walk that involves a shop at starbucks than A)dump her, B)screw her C)BRING her home or D) continue to your hottub
If you live in a rural area skip the second part.
Or you could just bring her out to dinne at a semiformal but inexpensive restraunt.  Tell us where you live and we could help you out better. And don't forget the chocolates, cards,  and all of the other LITTLE STUFF.