The intent behind this question has changed a bit over time. It used to be that I wanted to provide a long answer involving podcasts, blogs, rss feeds, ways to search YouTube for videos and explain the hazards of downloading "hacker tools" without looking through the source code first.
These days, time constraints are increasingly discouraging security professionals from staying informed. There are two many resources and too much noise to get through. Here is the solution:
http://www.hackerjournals.com
This is a clean, easy to read, noise free aggregation site that combines all of the above into one resource. Its still a fairly new site, so give it some time to fill in more content. But I highly recommend it as a book start page or favorite already.