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What a phenomenal and simple idea: eCards for your iPhone-carrying friends.
New service eCardlets, based in San Francisco, and founded by former Microsofties and Googlers, lets you create an eCard on the web, then send the recipient a text message containing a link to the card. You can try it with the Mashable card above, or a wide selection of other options.
The cards are specially optimized for the iPhone, of course, allowing you to open the card by dragging your finger across the front.