Apple also have an on-line 'refurb' store.
The good things about it are that warranty cover is the same as for a new Mac and, in general, the products appear to have been either immediately returned purchases or inventory that wasn't sold prior to a model change (rather than well-worn second-hand devices though, admittedly, that's based on a sample of 1; an iMac bought to use as a second TV/PVR).
The not so good are that the savings tend to be minimal, often they aren't for the latest versions of each model (look carefully at the specs) and they may not arrive in quite same packing as the new models (seriously, Apple packaging is a work of art).
In general I'd recommend keeping an eye on the MacRumors Buyer's Guide so you know when you can get your hands on the latest models, or when there are likely to be a few more of the current ones in the refub store.
(p.s. The next MacBook Pro, likely to be available in the summer, should be exceedingly good!)
BT Infinity? 'tis very good![]()