I was going to PM this to Sid, but I since others have asked, I thought I'd just post it. Here at the magnets I use:
These are the widest I use. I use these in the turret foundation on the top of model bases. They fit almost perfectly on top of the Shaltari skimmers. I also use them on the underside of walker torsos, where I attach them to the legs. I've used them in various other places as well.
I use both of these extensively. They're the same width, but one is taller than the other. The taller ones get used on top of the flight stands, as well as fitting perfectly into flight widget slots. I use them for smaller turrets, too, and other occasional random uses.
These are the magnetics with the holes in them. They're a good mid-sized magnet, and they fit into a lot of misc spots. I primarly use them as the bottom of turrets, trimming the resin tab and affixing them.