More and more resources for developers are being released lately by experienced developers. And they are free!. Excelent news.
There is a great and free magazine that you can download in .pdf: Methods and Tools. The articles in the last Summer 2009 issue are really good.
DZone Refcardz is the other great resource that I find very useful. They are small pdf cheat sheets containing different topics, covering several tools and frameworks. They are free too.