Check the alchemist's cellar; there is a book there, as well as some potions.
The mushroom the farmer is looking for is north west of town (as is the floogefrog killer). The mushroom you found gives a permanent +3 luck boost.
Have you been to the lich cave in the mushroom forest? The solution to the murder is there.
The imp hero is in the spider forest, north east of the village.
