The Undercover Economist A great introduction into the applications of economics to the real world without getting too abstract. See book review post for more.
Freakonomics: A Rogue Economist Explores the Hidden Side of Everything Similar in style to the Undercover economist but deals with more abstract issues. See book review post for more.
Thinking Strategically: The Competitive Edge in Business, Politics, and Everyday Life (Norton Paperback) A great primer for game theory. Be sure to read at least the first few chapters before your interview!
The Armchair Economist: Economics and Everyday Life Deals with some issues you won't come across until your first year at uni, and that's precisely why it's so great if you can talk about them during interviews.
The Tipping Point: How Little Things Can Make a Big Difference This has been put lower down on your to-read list as it's more about psychology than economics/business, but contains some great ideas to talk/write about.
Foundations Of Corporate Success: How Business Strategies Add Value Summer reading list (pre-1st year) book. Easy to read introduction to game theory and aspects of management. If you've got the time, go for it!
Organization Theory: Selected Classic Readings A lot like the stuff you'll be dealing with at uni from some pretty well known (you'll get to know them well, trust me) management theorists.
Thinking Skills (Cambridge International Examinations) An absolute must for TSA preparation