I feed my rabbits wild violets- they are everywhere in our yard. I don't know what species, but in the family Viola. this is a really good link on violets, it refers to them as edible for humans, but I know they are edible for rabbits too:
http://ofthefield.com/forum/showthread.php?tid=70
be sure to read the Caution at the bottom of the page!
I was wondering if anyone feeds wood strawberries (Fragaria virginiana) to their rabbits? We have a lot of them, but I haven't given any to the rabbits. They are in the rose family, so I think they are safe.
I also read somewhere that you should avoid giving the rabbits too much calcium and sugar.these were listed:
Broccoli (the whole plant) (high in calcium, also may cause gas)
Carrots (high sugar content)
Carrot tops (high calcium)
Kale (high in calcium, also may cause gas)
Mustard greens (high calcium)
Parsley (high calcium)
Spinach (high in calcium)
It listed carrots, so I'm not sure I can trust it...