how do I create a partition for SnowLeopard without wiping Lion?

[space-time]

I would like to keep Lion where it is and also install Snow Leopard. In the past I always had to erase the HD and make 2 partitions when I wanted to have multiple partitions.

I used Bootcamp once to resize a partition and install XP on the new partition, I wonder if I can do the same, and install SL on the newly created partition (and keep Lion) where is is but on a smaller partition?

Thanks