I manage an account for a cousin of mine and use Turbo Lister 2. Its pretty buggy and crashes sometimes, but it gets the job done. I generally only spend 15 minutes relisting a few hundred items every day. You can import and modify listings in it fairly easily as well.
Now answering questions from random idiots, especially ones like "OMG I PAID 20 MINS AGO IS IT SHIPPED YET???????????" - that takes more time...
Oh, and its free from eBay itself.