Google applications are a lot more efficient when you use the keyboard shortcuts. For example, in Gmail you can hit r to reply, a to reply-all, f to forward, j to move to an older message, k to move to a newer message and there are many, many more.
I had been using keyboard shortcuts for years before I discovered that hitting ? brings up an overlay showing every keyboard shortcut for the application. Check it out and learn as many as you can.
The ? shortcut works on Gmail, Reader, Calendar, and Rietveld. Other applications that have keyboard shortcuts are Voice and Wave, but ? doesn’t work in them. Instead, you can go to their help pages to learn the keyboard shortcuts.
In Gmail, you need to click on “settings” at the top right and turn on keyboard shortcuts before they start working.