One resource you might find helpful is the Design Intelligence annual rankings. It has some information, but it is not an exhaustive resource. Another thing to keep in mind is the manner in which they gather information and compile the results. This is far from a scientific survey. Basically they go out and ask a bunch of employers which students from which schools are they most impressed with.
Of course for landscape architecture, places like Harvard and UPenn are going to consistently rank high. In fact, Harvard is always the top ranked school in every discipline. However, Sarah’s point can’t be overemphasized. What’s most important isn’t getting into some school that someone you never met is arbitrarily assigning the label of “The Best”. What’s important is finding the “Best Fit”. The best course of action is to decide what it is that you want to study, then find schools that would best support you. After all, the schools are also looking for someone who fits into their program.
It is true, most deadlines for admissions into fall of 2009 have passed. Typically, the deadlines are between mid December and early February. But that just means you have plenty of time to research and prepare a stellar application for next year!