Keep your eye on your e-mail. If there is one place where the tools of Web 2.0 will affect your life, this is it. The idea of a customizable Web -- one that lets you create "mash-ups" of existing content and form them into tightly focused sources of information -- is making its way into the flow of our daily messaging.

Tomorrow's e-mail programs, many of them Web-based, will incorporate sources such as Web logs, wikis, instant messaging and RSS news feeds.

We already can see hints of this in programs for individual users and a new wave of business products.

Take a look at the redesigned interface that Yahoo Mail is rolling out. Now out of a beta testing period that lasted almost a year, Yahoo Mail's latest look includes ingenious shortcuts that put information over your messages when you need them.

Drawing on the mash-up notion, the additional data pulled from the Web can make your life simpler: A message from a friend asking you to lunch includes the restaurant's name and a time for the get-together.

Yahoo Mail now underlines addresses, places, dates and contact information with blue dots. So when you're not sure where the restaurant is, you can click on the information to pop up a map. Click on the date and up comes your calendar for a quick read on what's available.

This ought to remind you of the kind of mash-ups we've seen with mapping software, imposing data on a map to make it easy to extract more information from the display.

Google Earth remains at the vanguard of mapping mash-ups, with user-added overlays that can provide disaster information (think Katrina), travel images or even street scenes.

The idea of superimposed data streams is powerful at all levels. Extending them into e-mail through intelligent shortcuts lets you get more done from within your messages.

In a similar way, Yahoo Mail allows text-messaging to cell phones as an option, meaning that you can send and receive text messages from the same program you use to process e-mail. The service had already provided built-in instant messaging capabilities, so what we're seeing is an attempt to fold together popular communications methods.

Popular they are: 69 percent of mobile-phone users 18 to 39 say they use their cell phones for text messaging in personal as well as business applications.

Clearly, we're seeing how competitive is the turf upon which e-mail innovations will jostle for supremacy, and you can bet that companies in this space will have to adapt to the growing interactive tools of Web 2.0.

Yahoo Mail's integrated RSS reader is another case in point: Really simple syndication lets you subscribe to Web sites so that new material shows up automatically in your reader. This is especially useful for reading Web logs. It seems a natural step to fuse Web and e-mail reading functions into a single interface.

On the corporate front, have a look at Zimbra (www.zimbra.com), another e-mail option. Well attuned to the mash-up concept, Zimbra offers "zimlets," which add related information from within the company to basic e-mail messages. With support for Microsoft Outlook, Eudora and other mail programs, Zimbra offers a browser-based e-mail program of its own. Work within its interface and key information pop up as needed from within an e-mail message.

Perhaps you have received a message with a purchase order. Letting the mouse hover over that number, you would be given a description of the order and related financial information, all without having to resort to a company database or spreadsheet for further background.

Managers needing to make go or no-go decisions on such orders have the capability of viewing the entire purchase order from within the message or approving or rejecting it. The system is obviously extensible to shipping, invoicing, merchandise tracking and more.

Now, what's next?

How will these trends play out over the next few years? For one thing, we might need a new term for a program that not only handles incoming mail, but also connects broadly to data sources throughout the Internet.

Take a look at Tumblr (www.tumblr.com) to see a consumer-side aggregator for personal content. The free service lets you create a kind of Web log that is made up of any kind of media -- audio, video, photos, text -- that the user encounters on the Web.

That makes Tumblr a kind of blogging service, but note this: Tumblr also lets you aggregate data feeds from other sites you visit. Thus RSS streams from Web sites can flow into Tumblr, as can photos from community sites like Flickr, or bookmarks from del.icio.us.

The reality is that as we use the multifarious tools of Web 2.0, we set up an increasing number of information feeds, a multiplying online presence that can be confusing without somehow drawing it together.

So as Google, for example, eyes what Yahoo Mail and Zimbra are doing, it and other companies with major e-mail presences have to be thinking of adding hooks in their programs to resources that could be anywhere on the Web.

Web 2.0 is all about connections, something e-mail services have only recently begun to tap as users look for a common home for their data.

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