In the past I used to mess around with NFS over SSH but these days the FUSE options are much easier, except when you want to use a public key to authenticate with the remote host. In that case do this:
Actually, right after I posted this, I realised there's a better way to do it. That is, use the 'IdentityFile' option instead (as per the format of .ssh/config).
$ sshfs -o "IdentityFile=~/ssh_keys/[email protected]" [email protected]:/var/www/ ~/Sites/awshost
If you have any problems then add '-o debug' to the above command to help track it down.