The Oudaya was one of Moulay Ismael's smaller palaces.(He who built at Meknes to rival Versailles.) He subdued the pirate Republic in Sale and took over the Rabat Kasbah to keep them subdued. It was garrisoned by Sahari warriors who accepted military service in lieu of paying taxes.
There is a nice garden courtyard, replanted by the French as the "Andalusian Gardens" and the palace itself is now a jewellery museum. This is a little confusing as there are a lot of non-jewellery items in various books labelled as belonging to the "Oudaya Museum Rabat" which were presumably there in a previous incarnation. They now appear to be physically in the Archaeological Museum although they are still labelled as belonging to the Oudaya.
The Archaeological Museum itself is probably the best 80p you'll spend to visit a museum anywhere. It is very small but has some outstanding Bronzes and some greek-style stone carvings from the roman period to say nothing of a couple of neolithic skeletons. Sadly they do not allow you to take pictures.