NYTimes: NBC in Deal With Amazon to Sell Shows on the Web. Amazon Unbox already has a few NBC and Scifi shows online, including Heroes season 1 for $1.99 per episode—or the entire season for $31.99 (short of the $39.99 sticker price for the DVD box set).
Considering NBC has supposedly been complaining about the iTunes $1.99/episode price being too low, I don't think this is really what they have in mind for future offerings. But it's a smooth move from a PR standpoint: "Apple wouldn't let us charge a sale price for an all-season bundle of Heroes, so we went to Amazon to give you the bestest deals!" Pull-quote from the NYTimes article, from the president of NBC Universal Digital Distribution: "Amazon is a company that understands the value we provide as content owners to its business." I.e. "We want to charge more money."
Amazon Unbox doesn't work with Macs or iPods. It can do direct downloads to a TiVo, though.