Using a vacuum forming machine, I was able to make candy molds of LEGO men. They turned out very nice, and I'd recommend the project to anybody else. I made this at Techshop
Step 1: Create the Mold - 1
First, make sure that you turn on your heating element to warm up. Your settings will depend on your machine, but I left it on the default settings, which was a uniform heat, and about 80% power.
Then, you must create a mold layout. With the masking plate down, I laid out all of my mini figs. They will shake around a little bit from the platform going down and up. I might try attaching them to a large, flat lego surface, but you must be careful to not cover the vacuum intake. It worked pretty well without that, though. Keep them away from the edge by about an inch.
Then, lower the tray. Since they are plastic, I lowered it quite a bit to make sure that I didn't melt them.