The plans at the link are for a 3 foot floating shelf but adjustments can be made for a different length. This is a project you can complete in a day.
Seamless Floating Shelf DIY
Build a seamless floating shelf using the free woodworking plans at the link. Making the shelf seamless makes it look more like one solid piece of wood.
Build this unique floating ladder shelf which you would mount to the wall. Free plans at the link.
Stop putting holes in the wall to hang pictures, build some of these picture ledges so you can lean your pics.
Build a wall mounted crown moulding shelf using this free woodworking tutorial.
Easy to follow instructions to build and install an floating picture ledge.
Build a pair of these fun cloud bookshelf ledges using this free tutorial.
Build rustic corner floating shelves using this free woodworking tutorial complete with lots of pictures.
In this case, you will see how to build and install built-in floating shelves. Full instructions as well as a video.
This is an easy build and mounted on the wall, these floating bookshelves are awesome. Here are the free plans.