A new generation of communications software players are gearing up for what might be the most interesting race for market share since the browser wars between Netscape and Microsoft -- or at least since the race to distribute "push" products that happened a few years ago.

First came Third Voice, which has generated buzz over its concept of "Web notes" that allow visitors to post comments on a Web page. It launched its first version of its Web notes in May.

Now NovaWiz, Hypernix, uTok, and Zadu are launching software that follows the same idea. Hypernix's Gooey application launched in June, NovaWiz's Odigo launched yesterday, Zadu is expected to announce a Web notes product today, and uTok is launching on Monday. Many of these companies are taking the idea a step further than Third Voice by giving users more sophisticated tools for ranking, chatting, and exchanging information about the Web sites they're visiting. The goal is to enable users to build a community of Web commentary, separate from the Web at large, where users can share opinions and guidance on the content of Web sites.

PAN-WEB TOOL"It's a pan-Web tool," says Steve Jurvetson, partner at the venture capital firm Draper Fisher Jurvetson, describing the software genre. Draper Fisher Jurvetson invested $2 million in the first round of Third Voice's financing in February.

Each of the companies is taking a slightly different approach, even though they all hope to speed the uptake of their product through the distribution of a free, lightweight, downloadable client.

For example, uTok, which plans to launch a free, downloadable client of its product on Monday, hopes to address concerns about "Web vandalism" by implementing its Web notes as a separate window on the user's desktop. This makes the software more "site polite," according to uTok CEO Oren Zuckerman. Unlike Third Voice, which generates notes that pop up within a Web page, the user comments and discussions in uTok are relegated to their own distinct application.

"We don't mess up the page," says Mr. Zuckerman. "That has benefits to the site owners."

UTok also includes a rating system that polls visitors to any given page, ranking the page as either "thumbs up" or "thumbs down."

Hypernix's Web note-making tool, Gooey, falls somewhere between the products from Third Voice and uTok. Gooey pops up as a note on the Web page, but in addition to facilitating notes, it also serves up real-time chatting and ranking functions.

Of the entire group, NovaWiz's Odigo seems like the most ambitious. Like uTok, it also creates a separate application window on the user's computer, but rather than resembling an email application, as uTok's product does, it looks something like a futuristic remote control. Here, consumers can use the tool to "find like minds" by watching where users of similar tastes congregate on the Web. Users can also fill out identity cards and chat with fellow Odigo users. NovaWiz launched a beta version of Odigo on Thursday.

VIRAL RIVALRYWho came first? That appears to be Third Voice -- it was founded in 1998, while uTok and Hypernix were both founded earlier this year; Third Voice also beat the aforementioned companies in shipping product.

But such ideas travel in tight circles: Hypernix and uTok are both based in Israel, and NovaWiz also bases its research there. This is no coincidence -- Mirabilis's ICQ chat software was developed in Israel, and some of the officials from these companies aren't shy about the connection between ICQ and their viral software models. For example, uTok's Mr. Zuckerman says he is "close friends" with the founders of Mirabilis, whose software caught fire and was eventually sold to America Online.

Anybody who knows the Web, however, knows that coming first doesn't always matter. Because this is the battle of the viral apps, it will come down to which app inspires large populations of Web users to download and distribute the client the fastest.

The potential rewards for hitting a viral model, which typically refers to a software application that is distributed over the Internet and achieves an exponential growth curve, are huge. The most common reference points for viral apps are ICQ and the free Web email product Hotmail. Hotmail was sold to Microsoft last year for an estimated $400 million and now has about 50 million users.

The Web notes players are engaging in a similar game, and because the market share contest requires lead times of only months or even weeks, it's likely to be won or lost in the next few months.

"It's like there's a mathematical formula for growth for these viral apps," says Mr. Jurvetson. "All these companies are just now trying. Imagine you double in size every month -- if you start three months later, the difference between you is growing in relative terms. You're growing in exponential curves, but somebody could have twice as many users if they're just a month ahead."

APP NAUSEUMBut nobody can predict where a viral app will come from or whether it will take off, and some people have doubts about the category of Web notes.

"The only way it can work if there's some kind of intelligent discussion going on [inside the applications]," says Dave Winer, editor of Scripting News and president of the software company UserLand. Mr. Winer tried Third Voice and didn't like it, noting that Web comments become outdated as soon as a page changes. "My bet is that it won't take off -- but then again I said that about Hotmail, so I don't have a good track record," he says.

The business models for such sites call for them to be objective platforms where users can stand aside and watch the Internet, thus becoming high-traffic areas that can generate advertising and e-commerce revenue -- information brokers for the Web.

But one has to wonder, with a large group of these products now available, how does one decide between them? Will there soon be Web notes tools for the Web notes tools? The next craze could be meta-pan-Web tools.