For a long time, Noam Chomsky has been viewed as one of the big hitters in linguistics. It's probably fair to say that he's one of its most influential thinkers, widely admired for his groundbreaking ideas on language acquisition and what he came to term Universal Grammar. But in recent years there's been a growing body of research to suggest that his nativist approach to language acquisition - that all children acquire language through an inbuilt ability to relate universal rules of grammar to the language that is used around them - is on shaky ground.
The argument gets quite heated (and frankly, for me at least, almost completely unfathomable) in some places (like the comments that follow this Geoff Pullum THE review of a recent Chomsky publication) and I don't have the intelligence to follow most of it, but this is an interesting and readable account of some of the recent criticisms of Chomsky's approach by Dorothy Bishop on her blog and worth a read if you've already studied child language acquisition at AS/A level or are interested in finding out more.
There's also a really good chapter in the forthcoming EMC Language handbook, written by Paul Ibbotson of Manchester University, on new approaches to child language research.