Planetizen

I use this site mainly for its excellent compilation of news and articles related to the urban planning, design, and development fields. Their best service is the daily email newsletter, which gives you headlines and one-liners from some of the most important articles relating to planning each day. You can also customize the news to your location and area of interest. Definitely helps me stay current, and they also have original material such as op-eds, reviews, interviews, etc. which I always find interesting. Also leans toward the progressive side, which is a plus. :)