Most users of Lightroom really only use two modules: the Library and Develop modules. There is another module which is really fantastic but few people use it - the Slideshow module.
The slideshow module was added to Lightroom to allow photographers to easily create slideshow of their images, whether for professional or personal. You can design each slide, add your personal photography branding, add text overlays to express thoughts or memories, and even add audio tracks.
Once the slideshows are finished, they can be exported as videos, PDFs, or JPGs. Personally, I have created a few slideshows, and it's a very fun process. A couple of years ago I created a slideshow for a wedding album, so the bride could preview the layout in video format. It was extra special for her and made her that much more excited about her wedding album.
Below is a wonderful video tutorial by Tina from last year will give you a thorough tour of the the Slideshow module and hopefully encourage you to start making your first slideshow today!