We give dds, almost 9 and 5, a dollar a week. We don't hinge it to any behavior as we just want them to learn to manage money. We do require that they put half in their banks and half is for their wallet. Initially, I gave it to them in quarters so that they could see the division. Now, I give it to them monthly because I was forgetting it on a weekly basis!
Sometimes I dislike what they spend their money on, but I've already seen them learning lessons. DD8 loved buying sillybandz and Playmobil, but now is heartbroken that her sister (5) has enough to buy an American Girl Doll (allowance combined with monetary gifts for her bday).
Money is a tough issue for me, so I really want them to learn to handle it well. I grew up with allowance some of the time, and not others. My mom required that I purchase some things that I see as necessities at an early age (like a blowdryer as opposed to air drying my very long hair), and basic clothing. She would take me clothes shopping and tell me that I should really buy some things, that they looked so nice, and that she would loan me the money. I remember almost always being in debt and paying her off with Christmas money and babysitting (started when I was 10).
I very clearly saw that you had to work to get things, but always felt I was without what I needed/wanted and was in debt. Not how I want my girls to grow up. Restricting money by potentially linking it to chores can lead to anger, imho. I, like the other pps, feel that the girls should help around the house because we're a family and help each other.