Websites are great sources for info, but if you plan to really run around Japan, I'd advise getting a travelers
guidebook, the one I got was from the company "Let's Go Japan" it's got a website: http://www.letsgo.com/destinations/asia_pacific/japan/.
I recently went to Japan late September for 2 weeks, and I had the most amazing adventure in my life, and this guide
helped. I'm the type that likes to plan ahead of time, but also a spur of the moment kind of guy. So many times I
found myself at a planned site, whip out the book and say hmm this looks fun and detour myself there.
Also I'm a huge map guy too, and there really isn't any GOOD maps out there if you want to explore all over,
but the good news is that you can grab a map (many times in English too ^^) and plan your adventure on the spot.
I'd love to answer other question you may have, I'm definitely no expert but I am a Japan enthusiast
^_^
P.S. Japan was so fun that maybe I should go again next year and visit a Baka Bat (MT friend of mine) I did have a dream
of helping her move in maybe it'll come true XD... *side note - hmm wonder if she'll find me here, better not
be today you should be studying all day Baka ^_^')