1) Nothing beats the Bimmerpost homepage
for current news and features.
2) View these articles from the homepage for a history lesson: http://www.bimmerpost.com/classic/
3) BMW M history: http://www.m3post.com/forums/showthread.php?t=692266
4) BMW revolution from 50 yrs ago: http://www.e90post.com/forums/showthread.php?t=513815
And here's some history on BMW through videos: