Today I decided to play with something I had seen in a You Tube video from Joys life.com, which is embossing with my Cricut Expression. I just played and don't know if I will actually use this technique, but here are my experimental results. It was fun to try.
The blue sample is cardstock, which is so-so and the machine actually tore the paper a bit. The silver sample is foil paper and it shreds. The pink sample is Shimmer Sheetz and it does a nice job on that. The gold sample is thin metal foil which didn't give all smooth lines. Finally, the copper is thicker metal foil and embossed well. Unfortunately, you do get marks from the rubber rollers in the machine and there are some stray lines made by the blade as it moves to a different position and doesn't raise high enough over the already embossed portion. The roller marks can be avoided in your design if the design is small enough to fit between the rubber rollers.
To do this technique, you simply remove the regular blade from the blade houseing unit and then re-insert it upside down. You need to place some kind of embossing mat on top of your regular Cricut mat. The video I watched suggested a Spellbinder embossing mat, but since I didn't have one, I used some old Ellison embossing rubber. I am not sure if it is the same exact thickness. The material that you want to emboss is taped on top of this embossing mat and you put it into the Cricut machine and proceed as usual. Warning: This is not a technique from Provocraft, so it has the potential to damage your machine and void your warranty.