Use an editorial calendar in WordPress
Awesome, and very straightforward.
This is not a paid advertisement or affiliate marketing. I just think this product is really useful.
My friends at STRESSLIMIT have built a really nifty plugin for WordPress called the editorial calendar. It works exceptionally well at a very simple, but useful task. It helps you plan out your content with a very useful drag and drop interface. I checked it out a day or two ago and am already using the heck out of it.