Not thinking clearly, I threw some gelatin in a carboy before remembering that I wanted to reuse the yeast that is in there. Can I still reuse this yeast, or will the gelatin keep it from normal fermentation?

I would think you are SOL unfortunately. That gelatin will all settle to the bottom of your fermenter and leave quite a mess along with all of your yeast. I think it would be difficult to separate out the healthy yeast from the gelatin.

I think it will probably be just fine. You won't know unless you try.

Ah, dissenting opinions, gotta love it! I do have a pack of dry yeast laying around that is roughly the same type. I could try reusing my gelatin yeast and if it didn't take off in a couple days, pitch the (properly rehydrated) dry yeast. That should work, right?

I do appreciate any/all opinions!

You can always try rinsing the yeast to drop out the solids and see what's left. Also, another option might be to run the yeast through a starter and see what the fermentation/flocculation looks like and how much creamy, white yeast you get at the end.

I won't pretend to have any scientific evidence, but I've done this twice and it worked just fine. I did rinse the captured yeast with sterile water prior to repitching. Stopped doing it as I started just adding the gelatin in the keg.

Just an update in case anyone else suffers from the same lack of foresight. I ended up re-pitching the yeast. I assumed it wouldn't be too healthy, so I pitched quite a bit more than what Mr. Malty recommended. It started more slowly than usual, but after a couple days it was happily fermenting, and it finished right about where I expected.

Yeah, I figured that they would still work. The gelatin just assists in flocculation (clumping), but doesn't kill or deactivate the yeast.