The secret to remembering material long-term(bps-research-digest.blogspot.com)
bps-research-digest.blogspot.com
The secret to remembering material long-term
http://bps-research-digest.blogspot.com/2007/10/secret-to-remembering-material-long.html
http://bps-research-digest.blogspot.com/2007/10/secret-to-remembering-material-long.html
http://supermemo.com
(There are some interesting articles on sleep too, if you are not intimidated by walls of text.)
In my experience, repetition spacing seems to work for memorizing stuff. I'm less sure about learning skills- operative knowledge-, as opposed to passive information.