It looks like ShapeShift is back online, and Dash is available to trade again.

Although their "vacation" prompted me to try out that Exmo exchange's support for Dash's instantX (InstantSend?), and now I doubt if I'll use ShapeShift again in the near future.  I never thought that it would be faster to send Dash to an exchange, trade it for BTC and then withdraw, but it is.  And the exchange rate is better than ShapeShift, too (for small quantities).