It used to be that you could click on the Stack Exchange link on the top left of every Stack Exchange network site and would get a menu of links to other stack exchange network sites. Now it just takes you to the main Stack Exchange site. Why was this feature removed?
It's been moved to the right now:
There's a few other changes - which I talked about on this MSU post. It's been active a while so slightly surprised folks just noticed.
I ran into the same thing and had no idea that there was a stack on the far right of the top bar that now does that, until I saw the comment to the question. (Which should be an answer.) I was left without my normal way of navigating between sites.
For a while anyways, when you click on StackExchange in the upper left, it should say "Hey, if you're looking for the list of StackExchange sites, try the stack icon on the far right."