Firstly, a great interview with Will Wright on Spore and gaming in general.
Some great articles and videos of Spore devs talking about the programming mechanics behind the scenes:
There are lots of videos/articles demoing Spore's gameplay, but not as many that get into the meat of how the game was built. They're good reading/watching if you're into programming or game design.
Spore Gameplay Summaries: Cell Phase, Creature Phase, Tribe Phase, Civilization Phase, and Space Phase.
Basic, short video run-thrus of what each stage of the game is about. Each phase has different gameplay elements and different editing tools you can use to create personalized alien worlds. =)
And lastly, two great Spore blogs, which feature tutorials and other resources for aspiring creators: Spore Monkey and SporeTips!