bashcomplete

Here's a quick and dirty bash_completion script. Paste this in a file named "google" in your /etc/bash_completion.d/ directory:
_google() 
{
    local cur prev commands options
    COMPREPLY=()
    cur="${COMP_WORDS[COMP_CWORD]}"
    prev="${COMP_WORDS[COMP_CWORD-1]}"
    commands="help picasa blogger youtube docs contacts calendar"

    if [[ $COMP_CWORD -eq 1 ]] ; then
        COMPREPLY=( $( compgen -W "$commands" -- $cur ) )
    else
    case "${prev}" in
    help)
        options='picasa blogger youtube docs contacts calendar'
        ;;
    picasa)
        options='get create list list-albums tag post delete'
        ;;
    blogger)
        options='post tag list delete'
        ;;
    youtube)
        options='post tag list delete'
        ;;
    docs)
        options='edit delete list upload get'
        ;;
    contacts)
        options='add list delete'
        ;;
    calendar)
        options='add list today delete'
        ;;
    *)
        COMPREPLY=( $(compgen -f ${cur}) )
            return 0
            ;;
    esac
    COMPREPLY=( $(compgen -W "${options}" -- ${cur}) )
    fi

    return 0
}
complete -F _google google