Ask HN: Sales Resources

I'm working on a webapp that is targeted at will be directly sold to a pretty specific niche, like a 37signals app. I don't have much experience in direct sales, and was wondering if any of you had any good resources (books/sites/etc) for a beginner trying to get into the sales game. Your advice, tips, etc, you may have as far as marketing and selling an online service are all welcomed, of course. Thanks.

EDIT: It's targeted at the religious market.