Instant offline access to 130+ API documentation sets.
Super useful for quickly finding documentation for anything. Is often faster than googling and works offline.
Crowd-sourced code reviews on daily practice problems
I find this to be one of the quickest ways to get familiar with a new language. Work through the practice problems, get reviews from experienced devs. Allows you to learn quickly from developers who already use the language.
Short Screencasts of Gourmet Ruby
This format is great. Quick videos (try watching one a week). Each time you'll learn something new.
Learn to code on your iPhone
I love Code School because the video format is approachable. Plus - they have tests built in that make it easier to remember the content.