Playlist for WordPress is a WordPress Plugin that allows you to create playlists from your posts. A "playlist" is intended to be a collection of posts that for any reason you want to group together. When a user visits a post included in a playlist, the playlist will be shown in the bottom of the screen, if a post is not included in any of your playlists the playlist will not be shown.
Keep in mind that in this plugin all the playlists need to be manually created by the website administrator, if you are looking for a plugin that generate automatically a gallery of posts/custom posts/pages from a specified query check out Recent Posts Revolution.
As administrator you can create unlimited playlists by visiting Playlist, every playlist must have a name and optionally a description.
When your first playlist is done you can proceed to the next step and add items to the playlist, every item require a little thumbnail image that will be used in the playlist.
Once your playlist is completed visit a post included in your playlist to see the result.