This script ensures that ssh-agent is running and that my default keys are added when I launch the developer shell (through crosh or VT2) on my chromebook. The ssh-agent script itself is copied from http://help.github.com/ssh-key-passphrases.
I initially tried sourcing ~/.ssh_agent from ~/.profile (as suggested in gist 749325) but that caused errors when logging in via VT2 because the default shell for the chronos user is sh rather than bash.
curl -s -L goo.gl/VSVbH | /bin/bash
or
curl -s -L https://raw.github.com/chrisroos/chromebook-ssh-agent/master/install | /bin/bash
NOTE. The goo.gl shortened version is handy on my chromebook because I can't paste anything into the crosh shell.
NOTE. The installation script is pretty dumb. Running it multiple times will result in multiple 'source ~/.ssh_agent' lines being added to ~/.bashrc.