I'd heard of these penguin covers classics done by some comic artists but I didn't realise they had done this many so far. This link from eddie campbells blog.
you can view them here...
I'm filled with an urge to rush out and buy every one of these books for the covers alone (plus I should really read more than comics only so it'd be a good excuse)
Also the article mentions dharma bums, but have they done a cover for it? Crumb would do an awesome cover seeing how he's already covered the material...(cover done by Jason)