I am currently in the process of bonding my two lionheads. One of them has lived with another rabbit, but he died last year. I haven't had too much time to really make an effort, but did over Christmas and continued by letting them out together every day.
I orginally introduced them on neutral territory and then let them run in their room. Up to a few days ago, it only took a few minutes until I had to separate them and put one back in the cage. The time without arguments gradually increased and yesterday was the first time that they were out together for a good couple of hours without major incident (I just had to stop Charlie - the girl - a couple of times, but she now listens to a sharp no). I am really pleased with that.
Once they start interacting, e.g. grooming each other, sitting next to each other etc., I will take the separation wire mesh out in their cage and they can have the whole big cage together! I can't wait for that.
Here's some pictures of the two:
Charlie

Magic

As soon as that is done, I have another pair to bond... :P