Circular Crop Tool?

It's called a powerclip.

You can also try Object > Shaping > Intersect.

Create the circle and put it on top of your other object, image, or group of objects.
Select the circle and then Shift+click the object or group of objects you want to "crop", then use Intersect.

It doesn't work the same way as the Crop tool but it may do a very good job, depending on the objects and what you expect to get.
And yes, you can also use a freehand shape.