Is there one website that lists all the ferries that travel in Norway?
I've had the best luck going through www.visitnorway.com and then by region.
If you go to the English version of the Fjord1 site and then click on "Ferry Timetables" you can look up all of the ferries by region and route. I used this quite a bit last time we were there and it was a huge help!
How I would have loved to have such a website or timetable before our trip this past summer!
As it turned out, we never even needed it. Of course we had pre-booked the "big" ferry ride to get to Norway in the first place. But all the small ones, hopping over this fjord or that, well, those ferries just go back and forth all the time, and it was no issue ever getting across. Half an hour waiting time at the most.
Might be different if you are on a tight schedule or traveling off-season. But since these are the ferries the locals themselves use all the time, I would expect them to go year-round, weather permitting.