Slate is currently running a series of articles about how couples deal with finances. It is really interesting, and sparked a discussion this morning between me and BF about how we share our money.
We recently set up a "Yours, Mine, and Ours" system that is working out pretty well. We opened a joint checking account and each deposit enough money to cover half of our shared expenses. We also use the joint debit card for going out to eat and stuff like that.
This morning we agreed that when we get married we want to just throw all of our money together. The article about the "Common Pot" system on Slate dealt with our concerns and questions. A lot of the couples that they interviewed said they don't think about who spends what any more - like if the wife wants to buy new clothes or the husband wants to buy a new gadget (or vice versa, not to be stereotypical here!) they do not worry about keeping tabs.
I suggest reading all of the articles if you and your BF are talking about combining finances now or when you get married!