Hm. Let's see...I check out most of these on a daily basis (or, that is, I check out their gathered feeds):io9 - Maybe not a blog, per se, but still great for sf/f culture and science/geek newsSF Signal, of courseSF NovelistsLocusA Dribble of InkFantasy Book CriticPat's Fantasy HotlistFantasy LiteratureMagical WordsThe SFWA blogThe Night BazaarAnd those are just the genre ones. Got plenty more for science, geek, freelancing, publishing, general fiction/book interests, etc.
JV: Thanks for the comment.I follow a bunch of those, so I'll check out the ones that aren't already on there.Do feel free to suggest science/geek ones, though :)
Besides all JRVogt's recs (and I do read all of those feeds mentioned)Speculative Fiction JunkieDamien G. Walter's BlogA Fantasy ReaderGav ReadsPornokitschStaffer's MusingsElitist BooksDark Wolf's Fantasy ReviewThe World SF BlogWeird Fiction ReviewFantasy FactionFantasy Cafe
Here's a more comprehensive list:Writing/Publishing SitesDigital Book WorldRachelle Gardner's agent blogRMFW (local writing guild)TeleReadPublishersWeekly/Publishers LunchGeek/Science/Tech SitesGeeks Are SexyGizmagGizmodoLifehackerThe VergeWiredMashableTechCrunchFreelancingCopybloggerEntrepreneurFast CompanyFreelanceSwitchAdvertising Age
Nice ones, Adam. Spotting a few there I need to add on my end, methinks.