Tonglen isn't a very "Zen" kind of practice but I find it very useful.
I like that it can be practiced in a very simple and direct way in everyday life. Tonglen means "giving and receiving" and it's a method for connecting to our own pain in a way that gives it less of a selfish focus and helps us to develop more compassion for others.
It can be done very formally through an extended guided meditation (replete with "flashing bodhichitta") or it can be done on the run, or whenever it feels appropriate.
The way I see it, tonglen practice helps give some meaning to our pain so instead of wallowing in it and using it as an excuse to make an even bigger version of ME, we can instead use it as a tool to develop more sensitivity and compassion towards other people. So the pain that seemed so isolating and monumental at first can be transformed into something more useful that can help alleviate the pain of others. And the act of doing that ends up lessing our own suffering.
This short clip is from a dharma talk I did at a Queer Sangha meeting yesterday at the Interdependence Project.