NetVibes, the Paris based company that lets you personalize your home page with cool little modules that you can drag across the screen, has raised $15 million in more financing.

If you go there and play, you will see what people mean when they talk of the wonders of “ajax” technology.

Holy smokes, though: This is a lot of money for a company that hasn’t found a business model. It is one of the largest round of venture backing for a European Web 2.0 company.

The company raised a seed round in March. This latest round was led by Accel Partners, and included Index Ventures, which helped seed the company.

The extremely rapid adoption of NetVibes has enthused investors. This company has moved beyond the bubbly crowd of 50,000 or so experimentalists, and now says it has five million users. The numbers are going up almost a million a month, said a source close to the company. It is up from 2 million this spring. (Though we haven’t been able to confirm these numbers).

It has made more headway that the dozen or more other companies that are trying to do something similar. Microsoft’s Live.com is its biggest challenger. That giant had more than a year’s head-start over NetVibes, which was started by former journalist Tariq Krim. Live.com has about 300 modules you can select for your homepage, compared to NetVibes’ 200. NetVibes’ advantage is that it is agnostic, though. Recently, for example, it added the Web-based IM feature Meebo, allowing IM across platforms.

Pageflakes, backed by Benchmark, is the other serious contender in this area.

There is one little problem, of course. The company hasn’t found a way to make money. Its interface is so clean, it is like Google’s empty homepage. How do you interfere with users who have become accustomed to this? For now, we’re told the company isn’t yet focused on making cash, but is looking mainly to build the best user-experience.

Other seed investors in March included Netscape co-founder Marc Andreessen, European telecom guru Martin Varsavsky and Kelkoo founder and former Index Ventures investor, Pierre Chappaz, who has since joined the company.