I spent about 10 days in Hokkaido. Basically we stayed in Sapporo. There's lots to see but the best thing is the Sapporo Beer Factory. But don't make the same mistake as we did the first time and go to the
Sapporo Factory. Nearly identical name but this is just some shopping mall. Very confusing.
From Sapporo we made day-trips to Otaru and Noboribetsu. In Noboribetsu you should definitely go for a small hike to this volcanic mountain there (登別地獄谷). You just have to walk straight through the city and you'll find it. It has the only really natural hot foot bath I found in Japan and on top there's a small lake and some hot spring stuff. Definitely a must-see!
We also went to the Historical Village of Hokkaido (開拓の村) which is also very cool. More information
here.
In Otaru we wanted to visit the glass museum but we made the mistake and went to a restaurant where they brew german beer. We stayed there for too many Weissbeer and missed the opening hours of the museum. Actually it was not a mistake. The glass souvenir shop was still open.
I hope I could help out a little bit.
Stay tuned!