In March of 2008, I blogged about using vintage stamps on your wedding invitations. I really love this idea! I realize it would take a ton of time to accumulate old stamps, but I hear eBay has great sellers who specialize in just this thing.
If you are considering this fun project for your wedding invitations, or even save-the-dates, check out this FAQ page on US postage stamps.
[red envelope via Mrs Tulip; blue image via Martha Stewart)