This RedShark News blog post is an introduction to transitions in Premiere Pro for beginners. It's also an introduction to RocketStock's Stanza, a video transition pack for Premiere Pro with over 200 transitions. As best I can tell, Stanza's transitions are not effects, they're clips that you can lay over your footage in combination with the Track Matte Key and other effects in Premiere Pro. Cool stuff!
With Premiere Pro, you don’t need to be a seasoned editor to add seamless video transitions to your project. Whether you’re stitching together vacation videos for the first time or putting the final touches on your YouTube debut, it’s easy to achieve a professional look when moving from shot A to shot B. —RedShark News