I've been hearing about this for quite some time, and can now confirm it. Nick Rewind is a new "channel" on AT&T's new on-demand service called U-Verse. I hear they're showing classic Double Dare, among other things such as Clarissa and what not. The service is VERY new right now and is therefore hard to obtain. As far as I know, right now the viewer-base mostly consists of testers. Think of it back around 10 years ago when digital cable first came about and we were all trying to get GAS.
It's also sort of complicated to explain...it's internet-based, but you watch it on your TV. Essentially, it works just like cable, but the signal is brought to you by an internet cable instead of a copper coaxial cable. So, you need to have a special box connected to your TV to use it. But hey...
NICK REWIND IS ON THE AIR!
And for the skeptics, here's your proof: