20 Essential Gmail Tips You Probably Don't Use (but Should!)
Use Gmail as a Hard Drive

Every Gmail account comes with more online storage than you're ever likely to use (7GB and growing), or at least that's the case if all you're doing is using it for email. Rather than let it go to waste, why not use it as an online storage or backup for your local files? Here's how.

Download and install Gmail Drive from here. Gmail Drive is a Windows shell extension that creates a virtual file system based around your Gmail account. Once installed, Gmail Drive will appear as a regular hard drive under My Computer. Double-click the drive and enter in your Gmail username and password, and then just drag and drop files to upload them to your Gmail account. Of course, you'll need an Internet connection for this to work, since this is a cloud-based storage solution
When you log into your account, the uploaded files will appear as emails with file attachments.
Troubleshooting: Gmail Drive works best in 32-bit Windows. You can try your luck at getting it to work in a 64-bit version of Windows, but it likely will not work.
Our Top 5 Must-Have Labs Add- Ons
Gmail owes much of its flexibility to Gmail Labs. These add-ons are essentially beta services that, for one reason or another, haven't been implemented yet as a permanent feature. But don't let the experimental status fool you - there are a lot of good Labs features that both run stable and improve the overall Gmail experience. Here's a list of our favorite five, in addition to the ones we've already covered previously in this writeup (like Canned Responses).
Navbar Drag and Drop

Allows you to reorganize and reorder the items in your navbar simply by dragging and dropping. Very handy.
Forgotten Attachment Detector

Uh oh, did you just fire off an email without the promised attachment you said was included? That won't happen with this Labs featured enabled. Should you mention an attachment but forget to include it, a pop-up will appear giving you an instant do-over.
Mark as Read Button

Buttons or pull-down menus? If you frequently perform a particular action, the button wins out every time. And if you find yourself marking emails as read on a consistent basis, this just might become your favorite add-on.
Text Messaging (SMS) in Chat and SMS in Chat Gadget

Use these two Labs features together (the latter requires the former) to send and receive SMS messages in chat, which is a lot easier to do when you're sitting at a PC with a full-sized keyboard than it is to dig out your smartphone and mash your thumbs.
Undo Send

Probably the best Labs feature ever, Undo Send gives you a moment to reflect on that angry email you just sent your boss, and should a cooler head prevail, unsend the message and maybe even save your job!
Have a favorite Labs feature that didn't make the list? Be sure to post it in the comments section below!