If you Myst fans didn't know, Myst Online URU Live has been online for most of this year. If you want to still support Cyan, I'd recommend purchasing URU here on GoG and then downloading the client here:
http://mystonline.com/en and playing it. The development team is still patching it daily, from my last visit.
I've played a bit through the summer and acquired many Myst friends. The Ki is your messenger of sorts, allowing you to add friends as well as solve puzzles. If you can get a group together, or go with another group, you can solve puzzles that take hours to finish in minutes. It's a great environment for Myst fans, new and old.
I'm still working my way through to get to the Myst island for nostalgic purposes. I heard the books are burnt though. So no linking to my favorite Stoneship Age. :[