To donate
Just send a trade offer here:
https://steamproxy.net/tradeoffer/new/?partner=119624761&token=u4wHwLVc

Why donate?
Basically if you want to give back to the community for all the profits you made, you can donate. We typically redistribute items randomly to trade.tf users, except for metal and keys which we keep.
So if you want to donate some crates, weapons or anything you don't use, you're welcome and you'll surely make some people happy.