Palermo- must sees

I really don't agree with the concept of "must-sees", because interests are so individual. That said, these are sights of importance to many travelers:

Cathedral in Monreale (outside town, accessible by public bus, tour bus or taxi)
Norman (Royal) Palace (especially if you don't have time to get to Monreale, but worth it anyway)
Vucciria Market and/or Ballaro Market
Archaeological museum
Palermo Cathedral
Oratorios (chapels) and churches convenient to your other sightseeing plans.

Several people have recommended taking a street-food tour.

I consider the Cathedral in Monreale possibly the No. 1 sight on the entire island.

I agree with acraven, but here are the highlights for us:

Of course, churches are a dime a dozen, but we found the Church of San Domenico particularly interesting as it houses the tomb of Giovanni Falcone, one of the judges who won a series of convictions against the mafia and paid the price

Piazza Pretoria has a nice fountain and an interesting story -- nude figures directly under the windows of the Convent of Santa Catarina

The Norman Palace and Palatine Chapel - beautiful mosaics and moorish architecture. A nice, albeit smaller than Monreale, Christ Pantocrator makes an appearance here

Teatro Massimo, pretty good tour in Italian but echoed in English.

the churches of Piazza Bellini -- Santa Catarina, La Martorana, and San Cataldo (go in the morning; I can't remember the hours exactly, but not all are open all day)

A day trip to Cefalu is nice, if you have the time. If you must skip Monreale, be sure to get to the Norman Palace.

Monreale is the #1 site to visit.
Then Norman Palace, Capella Palatina, Teatro
Massimo, Palermo Cathedral and many open air markets.

Thanks! I have read and re-read Rick's travel guide on Palermo. I just wanted to check to see if there were places that people had visited that weren't included.

Well, there's a (ceramic) tile museum that I liked. Privately run. https://www.stanzealgenio.it/en/

Acraven--thanks for sharing. The tile museum looks very interesting! We will be in Palermo in May.

I should have mentioned that I discovered the tile museum on TripAdvisor--back in 2015 when it was easier to look at sightseeing options without a bunch of other junk on the screen. I've never trusted TripAdvisor reviews, but occasionally I would encounter a sight not mentioned in any of the guidebooks I'd looked at. Sights related to special interests like ceramics and glass are often overlooked by guidebooks because they're just not of interest to many people. For example, there are glass museums in Malaga and Prague and ceramics fairs in northern England that are a bit difficult to discover.