Which garden chemicals should I keep and which should I safely dispose of?

Q: I am cleaning out my garage and have realized that I have too many containers of garden chemicals – herbicides, insecticides, fertilizers, etc. How do I decide what to keep and what to get rid of?
Before sorting through a bunch of containers that may have chemical residue dripped on the outside, I recommend putting on a pair of gloves. This is not just for safety reasons. Some garden chemicals (such as malathion and some antifungals) contain sulfur compounds that have a foul odor that i