I got this bulb for free at Ace Hardware. It looks like a baby bulb and plant are growing out of the bottom. Is that going to be another bulb, or is it just a stem that is confused? I'm thinking of cutting it off and trying to make another plant.

Yes, it is a new little bulb growing off the side of your big bulb. Personally, I would plant them together. I love it when my Amaryllis grow multiple bulbs - it makes for a much better show when they bloom.

Some Amaryllis (like Butterfly Amaryllis) need to have multiple bulbs in a crowded pot to bloom.

I agree with Daisy, I wouldn't separate the offset yet, but leave it with the mother bulb to bulk up some more.
I also like the effect of multiple bulbs in a pot. If you want more bulbs they are cheap enough to pick up at stores.

Agreed too, keep the baby attached. If it grows well, eventually (years) it will bloom too or you may separate them.