Lots of people on here have suggested its a good idea to stay away from egg cartons...

Not sure about egg shells, though I have started tossing those into my compost pile (along with coffee grounds, and tea bags).

Seems to me you would have trouble putting drainage holes in the shells - or you would have to be very careful not to overwater - probably too much hassle for most people. You could buy some small plastic cups for a dollar or 2 - much easier to work with IMO.

I agree it'd be a big hassle. I have a feeling the egg carton would probably smell a lot less foul than when the soil heats up. You get used to it with time, but every year, once I fire up the mats and put the flats on them, the house stinks for at least a couple of weeks, IMHO. - although, it's not as bad as sterilizing soil with the microwave.

At Big Lots (an overstock outlet store) I can get 51 8oz foam cups for a dollar...

My mother uses paper childrens mouthwash cups from the grocery store.

But for sprouting seeds walmart/kmart/homedepot/lowes/etc have greenhouses for 5 or so dollars that come with peat pods... the greenhouse will support 72 peat pods (they have smaller ones as well). Some places also carry similar greenhouses that use soil instead of peat pods... those are nice as well.

I don't need a heater this time of year in sunny florida... But the heated varieties are I think 30$... Just make sure you get the kind that can regulate the temperature based on whatever you set it to, rather than the kind that simply heats up. else you might kill the seeds.

I used the cardboard egg carton before, bad deal holds to much water 80% died damping off fungus. Never again, I rolled on the cheap this season used baby food plastic containers and baby yougart containers poked drainage holes works great. Kept on the shelf above the DVR until seedling sprouted then put under lights.