As the vacuumcleaners dustbag fills up it get's slower and slower until it's finaly useless. Dustbags tend to be expensive, single use and at any time the manufacturer could decide to stop making yours, that is if the store still sells them.
Enter the resuable dustbag. It's made from an old T-shirt, a zipper, some vinyl and the piece of board from an original dustbag.
Slight update : This instructable got picked up on Hackaday. I'm so happy! :-)