My current one -- a 2010 Lenovo ThinkPad T510. A high-end, rock-solid machine with an insanely durable battery (they claim up to 8 hours on a charge, realistically I can pull about 5 or 6). Compared to a MacBook, it looks like the Tumbler Batmobile from Batman Begins, but it was about $1000 cheaper than a similarly specced Mac at the time of purchase; the keyboard is much better (not full travel, but good tactile action and nice concavities on the top that make them feel like real keys); and it runs Linux absolutely beautifully.