Dado Blades...

When I make shelving I find it quicker to keep the regular blade on my tablesaw, and then use a router and I personally nail a straight edge board across the piece where the router table will channel the bit into the correct spot and make the shelf notches super easy. This is also a good way to go if you're making a grid-like shelf - like cubbies or something, and have to stop half-way into the board.