Running contests and limited time promotions on your blog is one of the best ways to get people to want to come back to your site for more. Your newsletter could also help. You need to actively promote your newsletter and deals if you would like them to get more attention. One way to do that is by reminding your visitors who have reached the bottom of your site to sign up. These 3 slide-up plugins can help:
AWeber Footer Slideup: it helps you promote your newsletter without disturbing your readers. This plugin adds an AWeber subscribe form in the footer of your WordPress blog. The developer has plugins available for Feedburner and GetResponse also.
WP leFooter: adds a customizable slide-up section to the bottom of your site. You get 5 predefined themes and custom color options. This is a premium plugin.
Fancy Widget Popup: this cool plugin lets you add any widget to your sidebar and have it pop up when users reach the footer section. Use it to promote your social profiles or anything else you can think of.
You can also use Facebook plugins, Foobar, and other similar tools to promote your social media profiles, newsletter, and limited-time deals. You simply have many choices here.