Here is a list of websites and blogs with useful Magento information:
http://magento-quickies.tumblr.com/
http://magento-code-snippets.tumblr.com/
http://marius-strajeru.blogspot.com/
http://www.ecomdev.org/blog
http://www.yireo.com/blog
http://inchoo.net/blog/
http://maghelpdesk.com/
http://mage-page.net/
http://magedev.com/
http://magentoforum.blogspot.com/
http://prattski.com/
http://chasesagum.com/category/magento-tips
