I do think childrens charities such as nspcc, however i also think that animals get a raw deal at christmas.
Thousands are bought as presents and are thrown in to the street jan/feb time every year.
Animal homes burst at the seams in the new year.

small facts re battersea:
Battersea Dogs Home is a registered Charity that receives no Government support, so every donation is very well received to help us continue our vital work with lost and abandoned dogs and cats. It costs us over £8 million a year to run the Home - that means an average £637 for each and every dog and cat, no matter how long or short their stay.
http://www.dogshome.org/

also you have the ncdl
They never put a healthy dog down.
They have loads of ways you can all help, such as calenders credit cards sponsering dogs etc.
Our lovely dogs come in all shapes and sizes and are real characters, but the one thing they all need is a best friend like you. Some have really suffered at the hands of cruel and uncaring owners, making it difficult to find them a new home. Thankfully, these dogs are now getting the care they deserve at Dogs Trust.
http://www.dogstrust.org.uk/sponsoradogindex.asp?structureid=15

Sorry if i kinda went off a bit there, it just kills me evry year when i read the figures.
Anyway, those are my ideas, Im sure there will be enough to donate a little to quite a few different charites.