What happened to "Groups?"
They still exist--you can still add your instructable to a group.
The only way I could search or explore Groups was to click "Groups" on my personal page, then on the "Join other Groups" link at the bottom of the page. I couldn't find another way in (other than the advanced Search function.)
There doesn't seem to be a simple or straight-forward way to access them otherwise... I sure don't see a way to create a new one (not that a little weeding-out of the existing groups isn't called for.)
Edit: Oh, wait, I see it--you can Submit a new group.
But a lot of casual users probably aren't even aware they exist...