It’s really difficult to keep up with all the changes given that I work on Objective-C/Cocoa, Ruby, Android, JavaScript, and so much more. I subscribe to these email newsletters and allocate time to go through the changes and upcoming stuff. It initially felt like I was getting spammed, but over time, I found them to be extremely useful. Besides, these are weekly or monthly, so the frequency does not bother me at all. Check it out for yourself.

iOS/Cocoa
Dave Verwer’s iOS Dev Weekly – my Friday treat
Ray Wenderlich – monthly but sometimes more
Cocoaheads NYC

From Peter Cooper
Ruby Weekly
Javascript Weekly
HTML5 Weekly

Others
Haskell Cafe
NYC MongoDB User Group (via Meetup.com)