Another great idea from Stampin' Up! is the Envelope Punch board. You will have to wait until Nov 1st to order it though.  
It gives you sizes for 66 different size envelopes, and thats not all, it has two punches and also a scorer.  They all fit nicely into the board, so are always on hand.
It is small and light weight, it is a fantastic tool to have.
I have had so much fun using this, making my own envelopes, boxes, crackers, I couldn't quite work out the mini album though!