Rennet - is it possible to use vegetables?

Wow, thank you all

Or try one of these, where you wouldn't have to order a whole cheesemaking kit:
http://www.smalldairy.com, http://www.glengarrycheesemaking.on.ca, http://www.cheesemaking.com, http://eggplantsupply.com

There's a company called Urban Cheesecraft that puts out cheese making kits that use vegetarian rennet. http://www.artfire.com/users/urbancheesecraft

Google for vegetable rennet. But consider, even marshmallows, gelatin etc. Are made from similar animal products (Or which you really don't want to hear the details).
I don't think all but the most 'artisan' cheese makers create their own rennet.
It's available in tablet form from suppliers for the home cheese maker.