Hello! I retired from RS in the spring of 2011, and am now considering coming back. I'm sure that TONS has happened in the meantime, but what are some of the  most significant changes I need to be aware of? Back then I really enjoyed the Slayer skill and monster hunting, particularly DKs, God Wars, and Corp Beast. Thanks for any and all input! I'm heading to work, but will try to reply when I can.

Hello! The most significant change was the introduction of the Evolution of Combat. I would recommend going to the Combat Academy in Lumbridge and going through that tutorial to start learning, then set up your action bar and try Slayer, low level bosses (DK/GWD/etc., like you mentioned). There have also been a number of quests and new weapons released, along with a multitude of Dungeoneering rewards and the Invention and Divination skills. For example you can get rewards to clean up herb drops while slaying, bonecrusher + necklace for prayer point restore, charming imp to collect charms...anything specific you wanted to know? I'm not sure what else you may be interested in :P.