Flash cards are a popular way to test your information retention. While commercially prepared cards are available, the real value in any study method is in creating it yourself, so you digest and evaluate the information. Creating electronic flash cards lets you study on the go while still forcing you to carefully consider the information and how to encapsulate it on a single card.
There are a variety of other flashcard programs, such as Quizlet, Tiny Cards, etc. I suggest you take a look and find the one that works best for you
Mind mapping is a way of displaying information hierarchically, as with an outline, but in a more visual manner. It allows you to see relationships between topics more clearly, but oftentimes sacrifices some detail in the process. Space is usually a limiting factor in mind maps, which is why creating them electronically is so helpful. Two examples I've found useful are listed below.