While promotion isn’t necessarily sales or marketing it is definitely vital to branding and publicity and this is where giveaways and contests come in.
Rafflecopter helps you run these opt-in marvels from your blog. You handle the publicity and promotion of the giveaway or contest and Rafflecopter supplies the widget that provides the start and end dates, ways to enter, rules, etc. based on the information you decided on.
A great tool for authors and book bloggers!