Valentine's Day
Here's an interested e-lesson from the Economics America which is a good place to start:
http://www.umsl.edu/~econed/lesson2.htm
If you want to find out more about the different types of roses you can buy - and some cheaper alternatives for those on your B-list - you can read about them here:
http://www.flowers.org.uk/press/press-a%20rose%20is%20a%20rose-2006.htm
Here's a tip by the way, generated from personal experience, always make sure the flowers are delivered by a handsome young man in uniform in a public place when your target is surrounded by her friends so that she is making them all jealous by receiving them - it's worth the extra tip to achieve that effect!
Also, remember that a single red rose in a presentation box has exactly the same effect as a giant bouquet - and it's much cheaper.
Meanwhile, economist Brian Kaplan looks at why women bother with a man who has already shown that he can be unfaithful in his always excellent EconLog. In particular, he relates it to the lemons problem of imperfect information - except in this case of course, the woman usually knows that she is buying a lemon, so it's not quite the same thing:
http://econlog.econlib.org/archives/2006/02/lemons_for_vale.html
Perhaps Valentine's Day is summed up best by Russian economist Michael Kouliatvtsev:
http://faculty.philau.edu/KouliavtsevM/valentines_day.htm
And finally, if you're the sort of boring person who wants to find out who St Valentine really was, it's all here:
http://en.wikipedia.org/wiki/Saint_Valentine