Uncured resin

Silicone molds will resist some pretty good temperatures. One thing you might try is to leave it out in brilliant sunlight for several hours so that the sun shines directly into the mold cavity.  Both the heat and the UV in summer sunlight may help the resin to cure a bit further, which may help cleanout.

I'll try the acetone. It's a real mess. Thanks.

How to clean it up really depends on the mess. If by 'uncured resin' you mean 'has the consistency of raw honey', drain what you can into the garbage can, wipe the mold down in warm (not hot enough to warp the mold) soapy water and clean with an old toothbrush. 

If you mean 'formed a crystal lattice, but only part of the resin set up and it's a liquid mess with sizeable chunks of solids', try freezing the mold and its contents, then pull out what you can. From there, tweezers and dental probes can take care of some of the stubborn bits caught in the mold. Clean it with warm, soapy water.

If it's a case where the resin is thick and has the consistency of Jello and it just smears no matter what you do, remove what you can with paper towels and give it a light cleaning with acetone - but be careful because some low end RTVs don't play well with acetone. Wash and dry carefully to ensure every last trace of the bad resin before trying to use the mold again. Double check to see if your release spray is compatible with both the rubber and the resin before you pour and go light on the release spray.

I meant: How to get it off of a silicone mold?

JMorgan

Does anyone know a good way to get rid of it?