How long have you been gone for? :p
Quite a few things have been released. I'll start a few months back. The Void Stares Back quest was released which is considered a grandmaster quest. The reward is a Korski sword as well as 50 Void commandment points/tokens. The sword has a pretty powerful special which has basically took over pk'ing. A new make-x interface has been implemented which is helpful for a variety of things. New sound effects have been added throughout the game however, most noticeable is the combat sounds.... There... let's just say different. Thanksgiving and Halloween events were released as always. New Dungeoneering floors have been released (The Warped Floors) which I believe start at lvl 96. A new bank interface has been released allowing you to eat food/change gear/compare stats/add ess to pouches etc. while the bank window is still 'open'. Graphics have been updated allowing Mac/Linux users to use software mode. New task system evolved from the achievement dairys have been added and finally Herblore Habitat which I couldn't tell you much about as i have yet to do it.
You can always go to the Recent Updates and check things out
Welcome back!