I'm sure most of us have our favourite places / things to do in Japan. But maybe we don't all have the freedom (or finances) to travel round Japan for a month. Fabrice must be making a fortune from donations! Anyway, how about posting details of things that we've enjoyed in Japan?

Kyoto is the obvious choice for anyone coming to Japan, especially as the 桜 should be out in force in April. You can't really go wrong by visiting the famous temples listed in guide books and on the net.

My favourite is 天龍寺 in the Arashiyama area. It doesn't have the best looking temple but I found the serenity of the grounds (raked stones and quiet lake) to be particularly relaxing.

Gifu prefecture may not be a major tourist destination, but it's a major destination if you want traditional Japanese culture. Gifu has everything:
oldest sword making tradition (with museum and festival),
central pottery production (started several Japanese styles, several world-renowned museums, festivals),
ukai fishing (fishing with cormorant birds by torch, a national treasure),
Takayama festival (giant floats in traditional mountaint village, one of the Top 3 in Japan),
Nagaragawa fireworks (on of the Top 3 in Japan),
Mino paper (a main paper production site, lantern festival),
Hida bonodori (one of the Top 3 in Japan),
Shirakawa-go houses (a UNESCO site),
plus famous Hida beef, Gifu sake, more famous traditional crafts than you can shake a stick at (lacquerware, candles, paper carving, indigo dyeing, etc.)
one of the highest concentrations of ski resorts,
oodles of famous shrines, temples, and castles,
30min from Nagoya, 2 hours from Oaska/Kyoto, 3 hours from Tokyo, a few hours to either coast.
etc
etc
etc

I'd second dingomick's recommendation to Gifu - I had a fantastic weekend in Takayama and always intended to go back but never got round to it. Just taking the coach & train through the surrounding countryside was incredibly beautiful. The hida beef is well worth trying too! It really has a different feel from anywhere else I'd been in Japan.

Another non-obvious place I really liked was Inuyama, near Nagoya in Aichi prefecture. The (oldest original) castle and shrines that surround it were quite unusual. Nearby there's Meiji Mura, an open air museum which I found surprisingly interesting given I have no particular passion for architecture. There's also the Japan Monkey park and Little World (I think this is a kind of anthropology museum/amusment park) although I didn't visit either of these.