Santa Cruz Warhammer - John and Mike at Santa Cruz Warhammer have a real love for the hobby and it shows! They regularly give back to the community with free give-away's (one of which I won) and have great models to-boot.
From the Warp - Ron's great attitude about the different aspects of the hobby is very straight-forward and well thought out. (much like his projects) I like Rogue Trader Fridays, Ron's tutorials are great, and I'm always finding new blog to follow! With the semi-recent addition of a few guest authors this blog has growth in all areas. His blogger group now boasts "over 400 members" so definately "take a minute and see what's new."
Going on Campaign - This site seems to be at the forefront of campaigning for 40k. I could tell you all about the maps, markers, tokens, and campaign styles but it's simply something you'll have to take in yourself.
The Vanus Temple - Not only does this blog boast some of the coolest Deathwing models I've ever seen but the layout is simply gorgeous. Always a blast to read if you're into all the aspects of the hobby.
DEI GRECI - Described as an "Airmobile Imperial Guard Regiment for Warhammer 40,000", this blog features a project of immense proportion: an 'Athena Steampunk Airship'. Think huge and detailed. This guy carves plasticard for days.
Don't feel excluded if I follow your blog but you didn't make this list! It's not a definitive top 5, just stuff I'm enjoying lately.