If you want to sell digital products such as eBooks, templates, plugins etc. on your site then the WP e-Commerce plugin will do the job for you.
On adding the plugin you get a new admin menu called Products. Under this you first need to set up your settings. The free version of the plugin will allow you to take payments by PayPal, Google Checkout or Chronopay.
To get started with this plugin, you need to create your product groups. You can either have Categories or Brands, or both. So you could create a category for Templates, and a second for Plugins. Then once you’ve got your product categories created, you can move on to adding the individual products under Manage Products. For digital products you then upload the file when adding the product. This is then stored as an encrypted file on the server so that people cannot access it directly.
The plugin automatically creates the pages needed to display the cart on the front end. To alter the way the cart looks you can modify the CSS file in the themes directory within the plugin’s directory. You can have the cart to initially display a list of the Product categories or just display all the products available. There is also the option to have a breadcrumb trail display so that when someone clicks to view a product it will give them the trail at the top of the page to return to either the product’s category or the front page of the cart.
The great point with this plugin is that when someone makes a purchase of a digital product, they’ll be sent off to pay, eg. on PayPal, and then they’ll be returned back to the site and providing their payment has been confirmed they’ll automatically be able to download the products purchased. This means that you don’t need to do any work once your products are up for sale, besides the occasional update to the products!
Finally, there is a marketing section to help you improve your sales and offer discounts to people. You can create coupon codes for either a certain number of uses or to expire at a certain date. You can also add a cross selling feature, and also display the latest products added in your sidebar.
So, as you can see, if you want to get some digital (or physical) products up for sale on your blog to help make a bit of additional income, then it’s easily done with this free plugin. There are some commercial add ons as well, to give you extra features, however the free version does everything you need to get started 
I’ll give it try someday.
Selling products definitely gives you some additional income however you should choose the plugin to be used carefully.
I would rather suggest EShop. It is much easier to setup and can use wordpress posts and pages as products.
I have tried both but like EShop better.
I can be seen in action on my site.
Thank you for the post. I really want to sell something on my blog but I have nothing to sell.
Poor me!
Visiting this site for the first time…and you need to work harder to let people know a great site like this..exists…Only knew of problogger..but the information here is also valuable
its easier to setup.thanks for the trip.this product gives you some income .you should choose carefully.