This was actually not bad. Written and directed by Ti West, who also directed the sequel to Cabin Fever (though he's apparently disowned that).
The story follows this one chick, Samantha, who is a college student. On campus one day she sees an ad that simply reads "BABY $ITTER WANTED", with a number. She calls it and eventually takes the job. But there's more to the job than meets the eye (and all of that other hubbub).
It seriously was a good movie. Some people may thing a little drawn out, but I think it was paced just right. Really impressed.