Embellishing envelopes in some way is a widely practiced part of the art of sweepstaking. Some will take time to decorate the envelopes to their choosing, and others will want to forego the task, yet will still wish to have unique supplies to distinguish her entry from another. If you are one of these groups, here are some places you might like to look for those eye-popping, attention-getting envelopes and postcards.
Your local post office will have a variety of colorful and artistic post cards available, though as far as envelopes go, stamped envelopes are about as fancy as it gets.
Sometimes a print shop will have overage on envelope orders from customers that they wouldn't be using again any time soon. To avoid having to hang on to them, thus wasting storage space, sometimes they will sell these, either in one bunch, or as single envelopes, depending upon the amount they have left. These can run from around seven to fifteen cents a piece, or so.
You can also design your own envelopes and have them printed for you, usually for about this same price, depending upon the quantity you purchase, and what inks and paper are used. Find out more from your local printer.
The printed envelopes found here would often be of odd sizes, so would not do for entries that must be sent in a #10 envelope, though they would do nicely for any other. Though these are not something these stores will carry a lot of stock in, they can often be found in the clearance aisle, when they have them.
One of the most comprehensive sites for finding unique supplies (as its name states) is Sweepstakes Supplies. This site carries a good variety of unique envelopes, as well as postcards, pens, odd-sized blank entry cards, books, and more. There is also a monthly giveaway along with other drawings. Sweepstaking resources (such as judging agency listings), articles, and bargain-priced eBay auctions are some of its additional offerings.
For good old fashioned plain white envelopes to decorate at home, or to send out undecorated, I like to buy these in the bulk boxes available at any office supply store (such as Staples) for the best price on the relatively low quantity of 500 (usually right around six or seven bucks for basic envelopes with no frills). These types of stores will also have some pre-printed (or decorated) envelopes at a higher price, too, though there will usually not be much of a selection. You will have to decide if you prefer the cost-savings of decorating the plain ones yourself, or the time-savings of purchasing pre-printed envelopes.
I like to do both... sometimes I like to save time, whereas other times, I prefer to save money. Though I do also like some creative time.