Vacation, wooo! If you're headed out for a few days (or weeks or months), you'll want to inform folks who contact you that you'll be unavailable until you get back. Google Mail has a Vacation Responder that can do this for you. Check out the video or article below for how to set this up.
1. Log into your Google Mail account, click the gear icon, then select 'Settings':
2. Scroll to the bottom of the page and you'll find the Vacation Responder panel. You can set up what your auto-response will look like, when it will be sent, and who it will be sent to. The 'Last Day' feature is particularly useful, since you don't have to turn off your vacation responder off when you get back to work; it will happen automatically. When you're finished, click "Save". That's it!
A Few Notes and Disclaimers
When you set dates for your vacation response, your auto response will be sent until 11:49 PM on the Last Day that you specify. So, if you're planning to be back at work on August 15th, you'll want to set your last day as August 14th. The two checkboxes at the bottom are optional. I usually leave them blank, but you can restrict who will get your autoresponse. There's no way to set different autoresponses for folks inside the organization (like you could in Outlook); you'll have to be satisfied with a single auto-response. If you have Vacation responder enabled, by the way, Google will helpfully remind you of this fact whenever you log in, so you won't have to worry about leaving it enabled by accident: