I want to hang a 42" plasma from one of the overhead joist. This is nothing fancy, just looking to put it in front of treadmill then be able to rotate it to face the opposite direction in case the kids want to hook up the game console or dvd player. Every mount that I see would bolt in straight up, but I am looking for one that would go into the side of the joist. Any one have any ideas or recommendations. Thanks

Why not just nail (SECURELY fasten) 1 or 2 2x6 or 2x8's between 2 joists (assuming you have more than one) and then use one of the ceiling mounts shown here:
http://www.htmarket.com/home-theater-furniture-plasma-tv-mounts.html

That was my first thought, but wasn't sure about the stability. I think that may be my only option, I think it weighs around 60 lbs so that probably should work. Thanks

That was my first thought, but wasn't sure about the stability. I think that may be my only option, I think it weighs around 60 lbs so that probably should work. Thanks

Here's another idea if you're trying to mount to the vertical side of the joist:
http://www.sanus.com/us/en/products/visionmount/mount-adapter/VMCA5

Looks like it will adjust where your pole would be vertical/plumb with the joist.