Due to overwhelming demand (and "overwhelming" being an understatement), only the first 15,000 ornaments sold will be on Christmas trees in 2011. They sold 11,000 of them in like 5 minutes. [ PENS ]
And judging by the above graphic we pulled from the Foundation's site at 8:10am Thursday, it looks like the 15,000-ornament limit has been surpassed. But they're still available via the Pittsburgh Penguins Foundation.