All S&Ws have been drilled and tapped since 1990 or so. The holes are hidden under the rear sight assembly but you can see them from the underside of the receiver. A number of companies make bases, an aluminum weaver costs about $7, some rings (I like steel Burris Zee rings), the sight, and your good to go. I've got a 5" 629 set up this way with a 30mm Ultradot, it's a nice setup for deer.
A buddy of mine did his 686 with a steel Leupold base, Leupold turn-in rings, and a Millett Redot. It's nice set up too, he spent 4 times as much on the rings and base but it looks really nice.
B-Square and others sell no-gunsmith bases for just about any kind or handgun you can thing of.... though personally I think the drill-and-tap method makes for a better rig. -- Kernel