I like LWN articles, which are generally interesting and often cover technical topics that we don't know existed.

I also like some ACM queue articles, they are pretty in depth.

Usenix as well, while it is conference papers, I feel it has less noise than arxiv, and I am more likely to find an interesting paper.

Edit: John Regehr and Prof. Lemire's blogs are also very nice..

Any other similar sources?