What do you do with your old mobile phones?

With so many new mobile phones being released every month and technology moving so fast that it increases our need for another phone, what happens with your old phone.

For me my phones end up being given to the children to play with or just sit in a box somewhere.

I know other people who sell them on eBay, give them away as gifts or trade them in.

What do you do with your old mobile phones?