For the Florida resident (until the earth shifts!) a cold frame is a cheap, easy, temporary tool in the garden, usually made of plastic and PVC piping or any upright stake.
This blog has a very nice step by step and does not include a picture of me screwing bracket to my thumb!
For the favored plant in the garden that is well established, there are umbrella greenhouses and bell jars to protect them. You can also use a tomato cage as the upright support and a wrap of Visqueen as the protecting sheet. With all these methods, the greenhouse effect is in effect. You must tend to temperature and moisture under the cover. If it gets too warm in the afternoon, you will cook your plants alive!
You could even call the last minute blanket toss a cold frame. As I travel to work I see a lot of last minute thinkers trying to preserve their tender landscape plants from a sudden frost warning.
I have seen sheets with every super hero ever featured in a comic, sci-fi characters, and some very bold prints! It doesn't matter what the color, it does the job, but because these covers are not transparent and some blankets are too insulating, I have also seen more damage done with the blanket toss than the frost because the plants can't breathe and need light. If you can't get to your local garden center, Home Depot, Lowe's, Walmart, and Target carry breathable, lightweight reusable covers. I also found this pic from Bed, Bath and Beyond!