I have just joined Instructables and would like to know what an Orangeboard (in Instructables) is.
If you click on my name it will send you to my members page.
There you can see my stats, my profile, my most recent Instructables, and send a privet message, or send a patch.
Scroll down a little and you will see recent comments, scroll down more and you get to my Orangeboard where you can leave a public message and receive a public reply.
Follow this pointer to the bottom of the page
It's a publicly visible area for comments by you or to you as a member, which don't have to be tied to any particular I'ble or forum topic you've created. The name is meant to be a play on words for "whiteboard".