A really wonderful and thought provoking writer on photgraphy (and a terrific photographer himself) Mike Johnston recently had a nice entry of the itunes Jazz 101 on Sale on his blog, theonlinephotographer. It includes some interesting discussion as well. Mike's blog entry - Riches in Store. Given that these are priced below what itunes usually charges, there are some gems you cannot go wrong with.
One interesting quote: "A Love Supreme is many peoples' first Coltrane record, which is unfortunate because it then becomes their last. Not that it's not a great record, but it should be peoples' eighth or tenth Coltrane CD, and their 200th jazz recording rather than their second*.)"