1) Fuck Yeah Cartography! I don't have a tumblr, so I follow this via RSS. There are some truly awesome contributions that come along, even for folks who aren't map geeks. :)
2) Cake Wrecks. As a former bakery worker and someone who collected Wilton cake decorating catalogs as a kid, I love both the horrific mistakes showcased here and the stunningly beautiful cakes displayed on Sundays.
3) Feministe. I read a number of feminist blogs on a regular basis, but this is probably my favorite in terms of the mix of topics they cover, the sense of community and safe space that they provide, and how much I learn from not only the posts but the commenters.
4) Moda Bake Shop. I don't follow a lot of quilting blogs, and this one is focused on a particular company's products, so it's not the greatest, but it does have a lot of neat, free patterns and ideas.
5) Ask the Pilot. I'm also an airplane geek, and it's nice to get a commercial pilot's perspective on air travel, airplanes, and airports.
List one of your favorite blogs in the comments!