I recently started a group called Free Cakes for Kids Sheffield. There are FCFK groups all over the UK and we are one of the newest.
Basically, we (a team of amateur bakers from across the city) make birthday cakes for disadvantaged children in the city.
Children and families are referred to us by foodbanks, homeless charities and young carers projects etc. I just hated the thought of a child missing out on a birthday cake when I knew there would be people in Sheffield who'd find it so rewarding to make one.
There are 28 volunteers so far, a mix of mums who have small children, mums whose children have left home and miss baking cakes and people like me who just like to bake. We're having a meet up on 3 November 2013, so if you'd like to come along please let me know and I'll add the info to the thread.
All the info is on our website: www.freecakesforkidssheffield.com
So lovely local Mumsnetters: (incidentally I hope someone reads this as I know the local boards are a touch sparse), if you like baking and fancy baking one cake or one a month or one a year for a child in Sheffield, please get in touch. I don't mind how many or few you'd like to bake. 
Or, if you work with kids and families in Sheffield and think you might know a family we can bake a birthday cake for, please also get in touch through the website.