I will start it off with this:
I was searching for mirrored acrylic for a few projects I am planning. I was finding that it was quite expensive and often was in rather large sheets. Since my plan does not call for large sections I did a quick search for acrylic scraps and came up with many hits. This might be a good resource for all sorts of acrylic verities but it turned out that I found just what I was looking for, mirrored scraps.
The ebay seller is: http://stores.ebay.com/stoneedaze?_trksid=p2047675.l2563
If you search his ebay store for scraps (or ebay in general), you will get plenty of hits.
I ordered four colors of mirrored and he sent all that is in the photo below as well as a bunch of opaque black as a bonus. All sections have plastic or paper protective layers still in place. I paid $45 including shipping. For a scale reference, the flat rate shipping boxes are 5.375"x8.625"x1.625". He shipped them all in one box and gave me a $10 discount on shipping.
Fun item of note, I noticed that these were laser cut! You can see in the second photo the tell tail smoke trails.