This question has come up a lot lately and that is good because it really shows a resurgence in Domino development (or Notes as the case may be).
My answer is...it depends on your learning style.
If you want an immersive experience then come the http://xpagesbootcamp.com (DISCLAIMER: I am one of two speakers. If you do come I am not compensated any more or less but I will also tell you I would not mention the bootcamp if it had not already been very well received.)
If you do well in distance learning there is the TLCC courses http://tlcc.com.
If you well just figuring things out on your own then start with any of the great tutorials people have posted for free.
By all means, also buy the Matsering XPages book.
Good luck.