On a mac, if you do not want to keep passwords (or other data) in plain text in the config.rb, you can store it in the keychain.
Retrieve like this:
deploy.password = `security 2>&1 >/dev/null find-generic-password -ga account_name_for_password |ruby -e 'print $1 if STDIN.gets =~ /^password: "(.*)"$/'`
(Replace account_name_for_password with the account name for your password. )
A dialog will ask if you allow the access.
Instructions on how to add a password to the keychain: http://blog.macromates.com/2006/keychain-access-from-shell/
(P.S: Sorry about the ”Releases” category, but the forum system will not let me post without choosing a category, and no suitable category was available.)