MyYearBook, founded in 2005, just announced a $4.1 million round venture financing led by U.S. Venture Partners and First Round Capital.

The site has a look and feel suspiciously similar to Facebook (with a little MySpace chaos thrown in). Growth has been strong, with MyYearBook claiming 1.7 million registered users (mostly in the U.S.), and over 5 million unique visitors per month. The rumor is that MyYearBook has more highschool users than Facebook.

Mainstream press has given the site a lot of attention (see video below as well). Facebook was a year old by the time MyYearBook launched, however. And Facebook’s overall size puts MyYearBook to shame. If MyYearBook can keep its lead in the high school market, though, perhaps Facebook or someone else will acquire it before the next, much higher valuation, round.