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.
Easy to follow instructions to build and install an floating picture ledge.
Build rustic corner floating shelves using this free woodworking tutorial complete with lots of pictures.
Build a set of awesome floating corner shelves using the free tutorial found at the link.
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.
This awesome floating shelf is perfect for the entryway with its hidden secret storage compartment for keys.
This floating corner shelf could work beside a bed or perhaps by the front door. Here is how to build and install it.
If your TV is going to be mounted on the wall you will need something for the components underneath. Here is a great idea and free downloadable plans to build it.