Spaced repetition is a learning technique where you revisit previously learned material at certain intervals. There is reasonable amount of research that shows it working quite well. This is pretty much opposite to the normal cramming style I've used in school and university. While cramming the last few days before a test does give you good short term memory of the subject, the long term memory is not very good.

Obviously going over the same material by reading a book can be good option, but it is very time consuming. In spaced repetition you often just remind yourself about central concepts. Flashcards are obvious choice for this and there are many flashcard apps that use spaced repetition:

• Anki. Anki is open source cross-platform app with clients for Android and iPhone. It also has Ankiweb, that provides web client and syncing. Killer feature for me is creating flashcards on my desktop and going through them while going to work.
• Supermemo. I guess this is the "original" spaced repetition software and it does a lot more than just flashcards. Works only on Windows. The site does have a lot of indepth articles about learning and related matters.
• Mnemosyne. Anothe open source cross-platform app that seems quite good. I would use this if it had good Android client with easy syncing with the desktop software or some service.

I read a lot. Especially techical material about software development, usability and interface design. All that stuff is very interesting and as a bonus it is useful for career development of web developer. The thing is that I remember very little of all the stuff I read in the long term. So basically it's just entertainment or edutainment with very few benefits. I now aim to read bit less, but concentrate more on trying to actually memorize more of what I read. Writing short summaries and making flashcards for Anki will hopefully help with that.