How to speed my too-slow ssh login?

Edit your "/etc/ssh/ssh_config" and comment out these lines:

GSSAPIAuthentication yes
GSSAPIDelegateCredentials no

I had this problem and resolved it by turning off Reverse DNS resolution in SSH.

So in sshd_config on the server change this:

 #UseDNS yes

to this:

UseDNS no

Have you verified your DNS setup?

Try the setting mdns off in /etc/host.conf.

This disables the mdns resolution and helped me a lot.

EDIT:

It seems gentoo is handling this a bit different. To disable multicast DNS lookups, you have to change the file /etc/nsswitch.conf.
There should be something like:

hosts:          files mdns

Change it to:

hosts:          files dns