A while back we had a massive influx of spam signups - thousands per day, and at one point thousands per hour - that broke the thing that emails out confirmation emails and password resets.
I just unbroke it, and it's launched a whole load of wedged emails out. If you've already had your account activated and now get an activation email, just ignore or delete it. You don't need to do anything.
There are a bunch of folk who haven't been manually activated, so I'll get them sorted out next.