Let’s start with an expert artistic examination of some Golden Age Timely comics as recently republished by Marvel in hardcover.

http://timely-atlas-comics.blogspot.com/2012/01/usa-comics-vol-2-golden-age-masterworks.html

Here’s a good old fashioned fun Silver Age comic book, complete with horrid dialogue and go-go checks, starring the Challengers of the Unknown.

http://mailittoteamup.blogspot.com/2012/01/challengers-of-unknown-52.html

There is a ton of wonderful Marvel Comics original art posted here , much of it annotated!

http://themarvelageofcomics.tumblr.com/

Finally today, an interesting if not lately updated blog on digital comics coloring.

http://flatened.blogspot.com/