For me I really enjoy blogs featuring "covers" of classic comic work. The first one I started following is probably the oldest one — "Covered: Artists Re-interpreting Comic Covers" — which is pretty much what it says: artists doing a new version of an older comic book cover. Sometimes the covers are fairly close, other times they're a radical reworking of the concept. The next one I started reading is Repaneled which features artists doing a new version of a panel from an existing work.
Debuting this week is a new one called Cornered: The Cover Corner Art Blog which was started by Jon Morris. Self-described as "we recreate the spot character illustrations which appeared in the upper left-hand corners of so many classic comics, from Marvel to DC to Harvey, Charlton and beyond!" I used to doodle these character illustrations all the time as a very little kid. I think this is a pretty cool idea and I'm looking forward to following it.