The agreement with my fiance is similar to what some have suggested:
I make 80k after taxes, she makes 15k after taxes.
The house is mine in the Pre-Nuptual, however I must make all payments for it (which includes principle, insurance, interest, taxes and HOA). This amounts to 20k per year.
That leaves us with after housing, and after tax, incomes of 60k and 15k.
We put all the rest of our bills: Phones, Utilites, Insurance Car taxes, Food, Her College Expenses... into a pile, for which I pay 75% and she pays 25%. In practice, I pay for it and then she reimburses me for 25% after the fact. When we file taxes next year, we will file jointly, and split any return by the same 75/25 margin. Contributions towards our shared IRA will be 75/25 as well.
In exchange we split most common household chores 25/75 towards her.
Personal luxuries are paid for by the person who wants them. Dates and activities are 50/50 split.
This is a very new arangement, and I'm excited to see how it will work out.