Chegg's textbook rental business continues to grow like crazy - we've estimated 2010 revenues of $130 million, for example. And the company is now starting to acquire businesses complimentary to their core focus. First up is CourseRank , founded in 2007 by three stanford students. Total funding raised by CourseRank is $0 - it's "Mountain Dew funded to date," says Chegg. CourseRank helps students choose classes, and 95% of Stanford students use it, says the company.UC Berkeley, Duke, Cornell and other universities and colleges in the U.S. and Canada now use it as well. The company now has five employees.