My favorite Might as Well site was in Richmond, VA behind Acca Shops. During the merger days of pre and early CSX is was a hotbed of SCL, RFP, C&O, Chessie, and CSX paint of the month.
Depending on where I live and the nature of railroading in the area, my might as well site will change. I now have two, withing 20 miles, Aberdeen and Hamlet stations, NC. Aberdeen has three railroads converging into a spot of less than a mile. The mainline of CSX being one. The Aberdeen and Rockfish being the second with their engine house accross the CSX main from downtown. The final is the Aberdeen, Carolina, Western. When I might as well, I take a very clear route, depending on the direction I am coming from. From the north I turn into town on a certain street. I cross the CSX main and look for headlights. I procede for a block and turn either right or left. Left take me to the engine house, but as I cross the CSX main I can see if there is anything in the house, if none, I turn right a block and back to the CSX main and around to the interchange with the ACW.
I use a run through than on my way or there might be some action. I was doing some shopping and took a quick run through and CSX was doing some switching. He is the footage: