I've been cranking out a term paper on active learning in my natural language processing class. It's worth a mention here as well. Here's an excerpt.
Active learning is an approach to machine learning and artificial intelligence in which the computer guides selection of training examples. Instead of being a passive recipient of information provided by a programmer, the computer sends queries for the kinds of information that will be most useful and informative for the task at hand. In other words, asking questions for better information is part of the computer algorithm!
"Active learning" is also a hot topic in education research. Many of the ideas carry surprisingly well (What types of questions are the most effective? How should demands on the teacher and learner's time be balanced? What sorts of learning curves arise in practice?). Of course, in education research, the learners are young human students, not computers.
Here are two good reviews on active learning in machine learning (aka AI), and NLP:
(The figure above is from Settles' survey.)