How to safely dispose of extra chain lube I was trying to revive my old dirty chain for a few weeks while I waited for my replacement cassette to come in, so I partially soaked it in some chain lubricant.  What's the safest way to dispose of a small amount of dirty chain lube?
Depends where you are located.

Where I live in the US the county has a hazardous waste disposal facility that takes used oil - usually from people changing car and lawnmower engine oil.

As an aside, soaking a chain in lube to get it clean will not be very effective. Clean a chain with a de-greaser or solvent (preferably a  environment friendlier citrus based one), then re-lube.