Photo courtesy of http://www.spoonsisters.com/
If you are creative or crafty you're probably making your own invitations. But you still need envelopes. This template, available for only $16.95 from http://www.spoonsisters.com/ makes envelopes simple and easy. It allows you to create envelopes that measure: 4.5 inches W x 6.4 inches W; the template measures 7.8 inches W x 11 inches H, W x 0.1 inches thickness. It is an International Standard Size, Format: C6 and suitable for content format: A6 (or A4 folded in half twice). If you invitation is an different size you should be able to adapt the template fairly easily. Because it's made of wood it will last so you can use it for other projects after your wedding (maybe some creative thank you notes?).