Well, there's a wide offer. Casa de la Gastronomía Peruana is nice, though small, just for be there. More interesting are San Francisco convent & Catacombs, Santo Domingo convent (my favorite), Archeological museum of San Marcos univiersity (never been there, I'll go on friday), and the a Municipal Palace of Lima will be open (usually it is not), somebody told me it's beautiful inside, I won't miss the opportunity to visit.

There's a facebook page called "Lima Milenaria, Ciudad de Culturas". It has posted pictures with the entire list of museums.