Is there a DIY way to laminate things in my classroom?

Indeed there is. It is not quite as good as having a laminating machine but cheap "laminating sheets" can usually be purchased at office supply stores. Here's an example:

http://www.office1000.com/discount/laminating-sheets-self-adhesive.html

It's also called contact paper--you can find at office supply stores, hardware stores, or art supply stores. I have used it for quick and easy lamination of posters, etc. It comes in a big roll, so you can cut it up and use it for any size. Very handy.

use an iron with lamination paper...make sure to put a peice of paper between the iron and the laminate

option #2 sticky acetate film....no heat required

oooh - quick - go to Office Depot! They are offering FREE laminating for teachers every Thursday this August. You don't need a coupon or anything (so I heard - my school has a laminator so I haven't had to go to the depot yet).

For 8 1/2 x 11 sized things, I also like to use sheet protectors. The kind which are open at one end and you slip the paper inside. I use them a lot for directions to activities and other things that I want to be able to use again and again.