IIRC the sidebar used to have a link to the latest open thread, which I think was based on the open_thread tag. That seems to have vanished now.
I'm still seeing it, and it is tag-based, I believe. Changing the name seems to have made the links somewhat weird, though (it looks like both open_thread_march_14_march_20_2016 and open_thread_march_21_march_27 _2016 might work?).
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.