THE EXPERTS' GUIDE TO GOOGLE, YAHOO!, MSN AND AOL.

What if you went on vacation but left your hotel room only to go to one restaurant? Sure, you got a nice meal, but there was so much more to see and do!

Well, you probably visit your start page far more often than you travel, but if all you've sampled is its search, and maybe its Web-based e-mail service, you've really been missing out.

We at PC Magazine are frequent Net travelers. When we arrive at a site, whether it's new to us or already familiar, we frequently go exploring. And at some of our most-visited portal sites, we've noticed an impressive breadth and depth that's often barely hinted at on the home page.

To continue the vacation/geography metaphor, these sites are like pyramids. A trio (usually) of basic services sits right at the top: Search and Web mail, plus instant messaging. You can't miss these shiny capstones. These services are free, but choosing one â€" especially in the case of mail and IM â€" requires a commitment; people can't find you if you keep changing addresses, and you'll want to be on the same IM network (or networks) as your friends. So you want to pick carefully.

In the following pages, we review the search, Web mail, and instant-messaging services that the four largest portals, AOL, Google, MSN, and Yahoo!, provide. Now, a pyramid can be short and squat or tall and slim, but the next level down is invariably larger â€" and still in plain view. What makes up this level? Often, dozens of cool features that are just a click or two away from the site's home page. They include useful site personalization, strong financial tools and a broad range of discussion groups, and entertainment portals so engrossing they might draw you in on their own. But if your eyes zoom straight to the search box or Web mail link, you'll miss 'em, and we think that means you're missing a lot. As Web explorers, we've poked around this layer quite a bit, and we'll guide you through some of our favorite portal freebies.

Anyone who's played Tomb Raider â€" or heck, seen The Mummy â€" knows that some of the neatest stuff will be found in the catacombs, but unlike a pyramid's subterranean sarcophagus chambers, a portal's bottom layer contains not the dead but the nascent. There are some hidden treasures at these sites, in the areas called "beta," "labs," and "the sandbox." These places house new projects, programs, and capabilities that are not quite ready for prime time.

If you've got an itch to try stuff out before everyone else knows about it, you'll certainly want to poke around these out-of-the-way nooks. Our guide will show you how to get there and a few of the current highlights; but AOL, Google, MSN, and Yahoo! didn't become top destinations by stagnating. Expect the offerings here to change every so often, as projects like MSN's search clustering and Yahoo! 360° mature into main-page items.

The term portal may have gone out of style, but that's what these sites really are: not just destinations, but doorways. So, the next time you're at your favorite start page, take a look through new eyes â€" and keep this guide handy. You may be surprised at how much is right outside the search box.