Glad you asked (but, really, you’re here, so you clearly want to know).  WP Simple Seller is a plugin which adds a very basic “sell something from my blog” capability to WordPress.

• It adds a new type of page under a slug (the first part of the URL after “www.mysite.com”) which lists items for sale.
• It integrates into your existing theme, though you may want to do some tweaking.
• It allows each different author or contributor (“seller”) to establish their own payment credentials, so the owner or admin of the blog doesn’t have to get in between the seller and the buyer.
• It automatically generates a PayPal “Buy Now” button for each item listed (if the seller has PayPal credentials).
• It allows sellers to tag (categorize, technically) their items for sale just like they might categorize their blog posts, but of course under a different category hierarchy.
• It adds a widget you can use to show the categories of your sellable items.

Why Doesn’t It…?

There’s lots of stuff it doesn’t do.  Some of that stuff it may do eventually (and feel free to look at what I have planned).  Other stuff I just don’t think is in keeping with the term “Simple” in the name.  Like inventory control, for example.  If you want that, go get one of the other excellent e-commerce plugins.  This one is all about the simplicity.