Ask HN: Best keyboard-based productivity software?

I've been looking to increase my use of the keyboard, primarily for the productivity gains that I find myself able to reach by consistently sticking to the keyboard. Since I started though, I've noticed fairly uneven support across applications. For example, reviewing my day's worth of meetings and responding to each invitation using Google calendar is very painful to do on the keyboard.

What are people's favorite recommendations of keyboard-based productivity tools?