Google Labs, the research and development branch at Google, is always dreaming up wild and intuitive new services and improved versions of existing ones.  Typically those efforts are rolled into existing projects, or even occasionally released wholesale as a new service.

Gmail just received its second major Labs-inspired upgrade in the last couple weeks, following the rocky addition of Google Buzz. 

The new upgrade introduces six Labs features.  The first is the addition of autocomplete to the search bar.  The search bar will now automatically fill in email addresses or subject lines when you start typing in the search bar.  It also allows users to search using Google's labeling system.  The search upgrade currently only works in English.

Another useful feature is the forgotten attachment detector.  If you type a phrase such as "I've attached" or "attachments included" in your email and there's no attachments, it prompts you whether you want to add the forgotten attachment before sending the message.  That should save some embarrassing second emails

For those sending URLs, another improvement is the inclusion of a YouTube preview service, which converts URL's in Gmail messages to mini YouTube players.  Similar previews for Flickr and Picasa were not included in this update, but can still be found in Google Labs.  The Flickr preview reportedly works sporadically.

Another improvement is the inclusion of custom label colors.  And rounding off the improvements is a "vacation responder", which will automatically reply to your emails when you're away on vacation.

Google also took the opportunity to throw out some Labs candidates that didn't seem so good.  It tossed fixed-width font; muzzle, which trimmed chat contacts' status messages; e-mail addict, which imposed a 15-minute screen block to get people to take a break; random signature, which dropped quotations into your e-mail; and location in signature, which would add your computer-detected city and country to e-mail.  

Most of these drops seem like good ideas -- the e-mail addict certainly could get annoying, and the location in signature was a privacy nightmare.  The only one that was a bit disappointing was the loss of the random signature, which if done well could have been pretty fun.

For Labs users many quirky additions still remain, including Back to Beta, which restores the "beta" tag that Gmail long carried.  They can also fire up a quick game of Old Snakey, a web rendition of the popular cell phone/calculator game/classic computer game.  And there's also the infamous Mail Goggles feature that makes you do math problems before you can send late night emails to prevent embarrassing drunken messaging.