Note to self: whenever you have problems with SSH authorized_keys not working, check the permissions on the directories and files. Here are some quick instructions for getting SSH authorized_keys working on a new host:
ssh to the remote host and:
chmod 700 .ssh
Back on the local machine:
cat .ssh/id_dsa.pub | ssh remotehost "cat > .ssh/authorized_keys; chmod 600 .ssh/authorized_keys"