Peter has done a super job of describing how he has used servos to throw switches on his layout - see:

http://model-railroad-hobbyist.com/node/25958

I would like to suggest an alternative method of using controlling the servos.

I have come up with a simple modification to an eBay servo tester that turns it into a unit that is well suited to operating switches and comes at a very attractive price (I paid $1.24 for the controller including shipping to the US)

This is an update to my previous DCC Electrical Fun post.  While looking for what I could use for dwarf signals in the Union Station area (the ready made ones are kind of expensive), I found an item called an LED Assembly.  They are essentially two bi-polar 3-lead LEDs in a plastic housing.  They are a good size for N-scale or HO use.  The first picture below shows the first one installed in the Union Station yard.  The second is a diagram that shows how I wired the LED assembly.

I've got my third phase benchwork complete and most of the track down.  Just one more turnout and a few lengths of flex and I'll have all of the mainlines in place and operational.  I've been running trains around the upper level and everything works great.  My EM-1 will easily pull all the cars I own up the grade without even breaking a sweat.  And with quite a few hours running now no derailments anywhere on the layout.

So to complete the track work for the locomotive servicing facility, the Rutherford Yard industries including the wood chip mill I needed to install the extra track feeds to the track work.