The first way to learn something quick is to visit Merriam-Webster's website and check out their Word of the Day. If you were to do this every day for a month, you'd learn 30 new words. Or 365 over the course of a year.
Another way is to go to Wikipedia and click on their Random Article link. This second tip is from Chris Guillebeau's book titled The Art of Non-Conformity. It's amazing how much a person can learn just by doing something random.
Does anyone else have any other links or tidbits for learning something that takes less than half a minute? Please share your thoughts on the comments below.