Here is a great way to make a doll stand alone- NO hidden doll stands, no rods up the leg.
All you need is a super magnet!
These magnets are really, really small and super strong. You can fit them inside of a doll's foot, before you stuff the leg up full. NAIL a nail with a big flat head into a block of wood that you want to use as your stand, and WALLA! Your doll will stand unassisted.
Note, however, that you still might want to put an armature in the doll's legs so they don't get wobbly. Use a chopstick or some kind of bendy armature if you want to pose your doll.
I have never seen these type of magnets in a store, but you can find them in geeky gadgety online shops. Just google "strong magnets" or some such thing.