lifehack.org - perhaps one of the most under-rated sites of its kind.
They offer up advice and tips on how to make the best use of your time and how to accomplish things without spending a fortune. They are also are platform agnostic and always recommend interesting and helpful apps for Windows, Mac, and Linux users to try out, though their focus is not on software.
Content is upbeat, lively, and constantly changing. And when we say constantly we mean it, every day they seem to post yet another useful essay or article. Really great stuff, and written always in a straightforward non-hyped way, with almost no fluff -- these guys are serious about helping you improve the way you spend your time. Check out their site and sign up for the RSS feed and start hacking yourself!
