One of the most important parts of continuing learning as a DBA (or probably an IT Professional) is reading blogs. The world used to run on professional magazines and journals (and there are a few good ones still out there) but the current equivalent of a weekly or quarterly periodical is a daily/weekly blog produced by anyone from a corporate presence like Microsoft or SentryOne to individual DBA's chronicling their IT journey (like me)!
I used to rely on the Blogger Rankings from Tom LaRock as a good list of general SQL Server blogs, but recently I noticed the rankings list has been removed from his site. I don't know when it happened but since I frequently referenced new blog readers to his list I figured I should try to recreate a version of it myself.
These are the blogs I most frequently read and reference, although there are many, many, more out there.
I use feedly as my tool of choice, adding the individual links to my feedly so that all of the blog posts aggregate in one place.
As with any blog posts, read at your own risk and your mileage may vary (and remember, #ItDepends) but these are sources I find to be generally reliable, sorted by their employers for ease of reference.
Even though the blogs are broken out by employer, most of the posts (by far) that you see in these blogs are general SQL Server knowledge and *not* company product marketing (although those sometimes appear as well - for example you will see references to the new version of Plan Explorer Pro on some of the SentryOne blogs, etc.)
Hope this helps!