While magazines and newspapers head into the red, the textbook industry seems to be heading into the green these days. Online textbook rental startups are gaining momentum, and Kindle is looking to bash down the doors on a new e-reader textbook market in 2010. And thank goodness. It’s estimated that 4 million trees die untimely deaths in the name of the textbook each year. Not to mention the outrageous fees students pay for books.

Sign of the times: NYT tech blogger Miguel Helft reports that silicon valley giant Dan Rosenweig – former CEO of Yahoo and then chief executive at Guitar Hero – has signed on to steer a new ship. He’s joining Chegg.com, the online textbook rental startup currently leading the burgeoning new market. If Rosenweig thinks textbook rentals are the wave of the future – even if not primarily for environmental reasons – I’m inclined to agree. And I don’t even play Guitar Hero.  

Chegg.com grew exponentially last year – sevenfold, in fact – which would seem to be a significant indicator for the market at large. The company is up to 2 million books rented out to students (they’ve planted a tree for each of those 2 million, by the way), and 6,400 campuses reached. So far. Competitors include online rental companies like Book Renter and Campus Book Rentals.

Of course, the greenest and probably cheapest way to share/rent textbooks is still to organize an inter-school swap at your own institution, so that you’re getting your new American History text from your friend right down the hall (who just took the class you’re about to start) rather than from Joe Shmoe ten states away. But if Netflicks – to which Helft compares Chegg.com’s model – is any indication, online rentals will continue to overtake more grassroots swapping efforts.