I'm not sure there is such a thing on this site, since if it were used by a player to receive computer assistance during the course of his games, it would surely constitute cheating.
set up position?

I don't think that's the reason it's not available. It would certainly make it easy to detect when someone was using it for that purpose.
I think it's probably the result of Little Chess Partner being an application not developed by chess.com and simply not having this ability.
If this were to be added it would probably be via the same interface that drives the "Computer Workout" here. In fact, I think it's a great suggestion -- the ability to spawn a "Computer Workout" session from a preset position -- especially if it could be spawned from the ad-hoc analysis board since then a position displayed in the forums could be set up like this in two clicks (Diagram->Analyze->Play White/Black Against Computer).

TheGrobe said:
I don't think that's the reason it's not available. It would certainly make it easy to detect when someone was using it for that purpose.
Really? How?

Log the positions people set up and then compare them to the positions in their games at the time.
Let's say I study at home and i change my starting position, my strategy and so on...or I have a bad/good day when i play good and my concentration is at maximum...that makes me a cheater? What TheGrobe said is real - play with the computer and you will se some hazardous/curious moves or piece changes (knight for a pawn for positional gain and so on) and you will recognize that's cheating.
My opinion.
Is there somewhere on this website (or another one if not here) where I can set up a position and play against the computer?