Here's some great tutorials just in case your new and would like some more info on making fabric postcards.
http://www.quiltingboard.com/blogs/h...rd-b12455.html
http://www.quiltingboard.com/member-...t255514-2.html (comment #21)
http://www.patchworkposse.com/lets-t...card-tutorial/
http://debrichardson.blogspot.com/20...ebr-style.html
And, countless other tutorials on by Google and Pinterest and also here on the QB.
Sources for clear envelopes.....
http://www.amazon.com/100-Resealable...iglink21164-20
http://www.cellobags-clear.com/cellobags/L6B.htm
I also have found 4 x 6 clear sleeves at Office Depost in the photo dept. Although, these are NOT as good a price as the above.