Information on Hyperacusis and Misophonia
For me, the most important website was actually the Wikipedia entry: I made a printout to show my doctor (then she took me more seriously and gave me some tests to rule out the worst possibilities - whereupon it's easier to relax!)
I recommend to learn as much as possible about the possible causes and nutrition.
I will try to keep track of websites and books and things I found helpful here.
Another valuable resource: hyperacusis.net and hyperacusis forums. Very helpful and supportive community, wonderful people, information and forums could be a bit better organized (you need to search for more about nutrition etc. through some older archives to get info). Most people there recommend a certain treatment that may or may not be available in your country, or most appropriate for everyone (depends on the cause of your h.!), but everyone can learn A LOT from the tips and info on 'everyday' situations!
Nutrition and Sound Sensitivity
I first became aware of a possible connection between nutrition and sound sensitivity through the awesome ctds.info. There are some other good sites out there too.
My hyperacusis is nutrition-related: it gets worse if I'm hungry (or upset, also depending on the weather or time of month somewhat).
Things can get worse if I'm lacking some important vitamins/minerals like magnesium, B12, zinc, B6 etc. (I was vegetarian-ish before, I'm not anymore. I eat meat 2x a week or so, though I'd prefer to be vegetarian or even vegan - but since I was chemically sensitive and allergic to iffy artificial food additives as a kid already, and didn't tolerate the supplements well, I went all-natural again.)
We are all different and different lifestyles and metabolisms mean different nutritional needs.
If you want to track your nutrition, I highly recommend fitday.com. It was very helpful to see that I had vitamin/mineral deficiencies even when I thought I was eating healthy!
