Acetate, transparency, window sheet...all the same thing, just different thicknesses, etc.
Go to Beate's great tutorial on Shaker Cards (aka shaker boxes) to see an awesome use of acetate. See the tutorial on Acetate and Tissue, too! Those tutorials got me started with acetate.
-I stamp on it all the time with StazOn. Sometimes I color the back with a Krylon 18kt. goldleafing pen, and it looks soooo pretty.
-I also stamp images on the front, and then paint the back like a coloring book with PearlEx mixed with Future floor wax. (I use an aquapen filled with Future, but you could mix up a bit of PEx and Future on a little palette...scrap paper, plastic lid, etc.) After it dries, turn it over, and voila! It's gorgeous.
There is a sample of the Krylon (it's the Asian "Love" card) in my gallery, as well as a shaker card and an acetate tissue (although I must say THAT card is much, much prettier in person!)
ReindeerTrout recently hostessed a Asian Swap, and scans of the cards are in her gallery. Mary and I used PearlEx on the back of acetate that was stamped with StazOn, but we used different techniques...she sponged the color on, while I painted with a brush. Different looks, but both cards are very pretty.
And, yes, you can emboss on the acetate!