My children get a small allowance, but it's not based on their chores. I feel that if it was based on chores, it would be teaching them to expect something for everything. Keeping our homes clean is a job that must be done, regardless of monetary gain. Learning to be proud of it in it's own right is much better.
I started doing it because it's teaching them responsibility and because I got tired of them asking if they can have something at the store. Now I simply ask if they have their money and if no, then it's the end of the issue. They pay for their own stuff or if previously agreed upon, we will split the cost depending what the item is. My children are still pretty young, 8 & under, and their allowance is based on their age; one quarter per week per year. So for instance my oldest would get 8 quarters a week which just about rounds out to $8 a month depending on how long the month is.
When they receive it they're required to put some into their piggy banks, a small amount aside for charity (they like putting change in the Humane Society banks at stores, etc.) or Church and the rest is spending money. If they have critters, they also have to give me a small amount to help pay for feed and other supplies. They have also been encouraged to set up goals. For instance, my oldest daughter (6) decided she wanted fish. So she's been saving her money so she could get the equipment. She's learning thrifty shopping because she managed to find a really nice glass bowl at a thrift store for $2 vs. the $15 bowl she wanted at the pet store which enabled her to buy some other supplies faster. It's also taking her awhile because she had to help finance some little extras she wanted for her hamster. They weren't necessities for the creatures existence so she had to pay for them herself. My oldest boy has been saving his money so he can get a guinea pig. All three of my older children financed their own 4-H fees.
Also, if they break something on purpose that belongs to one of their siblings they have to either pay to replace it or pay the equivalent to the owner of the object they destroyed. (We don't pay retail for hardly anything, all of their toys are from thrift stores which is why I'm able to do this with them.) It teaches them responsibility for their actions. I've seen many less broken toys now that they know that if they break it, they'll have to pay to replace it. Toys are a privilege, not an entitlement.
Sometimes they get money at holidays or birthdays but we've taught them this is not the norm so if they do receive something, awesome, but if not, oh well. It's much more appreciated that way and they don't feel like it's an entitlement.
As for chores, they do get fined if they don't do a job properly on purpose. (Such as shoving everything under their bed or not putting their clothes away and just throwing them on the floor) because this can cost them time as well as supplies (so money). It's rare this happens though but when it does it depends on the child and the chore as to how much I might ask them for. It ranges from a penny to a quarter at a time, from their spending money. They're learning that way it's much better to do their job properly and on time than to procrastinate or not do it well in the first place. This also works every time I hear foul language from them. They automatically get fined $0.10.
The first time we did this, I wasn't very consistent until I actually started putting that amount into my budget. So at the beginning of the month when I withdrew money for the weeks expenses, I automatically withdrew their allowance money as well. Sometimes I might forget or might not make it to the bank when I like (We're on foot and my bank is across town; I'm also in a cam boot right now so walking distances are limited.) so I keep a running tally and then apportion it properly when I do finally get to the bank.