SSH Without Password

user1@host1:~$ ssh-keygen -t rsa

Generating public/private rsa key pair.
Enter file in which to save the key (/home/user/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/user/.ssh/id_rsa.
Your public key has been saved in /home/user/.ssh/id_rsa.pub.

ssh-copy-id -i ~/.ssh/id_rsa.pub user2@host2

source:

http://www.debian-administration.org/articles/152