The Magic: the Gathering Proxy Deck Builder has moved to:
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Copy and paste a decklist into the form to create proxies for the entire deck.
You can also specify which set to use for each card. When your deck is built on the next page, put your mouse over the card's picture and you can change the set.
Then print out the proxies, cut them up, and insert them in card sleeves over junk cards and voila! You've got a deck suitable for casual play or competitive testing.