Some of you may know that I believe to understand aikido (as a practical martial art) you need to understand the training method (see my signature). Now, there have been many recent advances in karate, trying to regain the techniques etc that have been lost in kata and change the training so it is more practical. Suprise suprise, similarities to aikido training method and also aikido technique is occurring. A karate friend of mine pointed out these two free online 'books' at this site which are well worth reading.
Now obviously this is for karate and I personally would not do everything within these books (though Iain Abernathy seems a bit of a dude), but they detail very effectively the reason behind different approaches to training. Hope you like them.