The main shopping street (by Cuban standards) or street with the most activity is the pedestrian part of Avenida 54 to the west side of Calle 37 (Paseo del Prado).
There are some US dollar shops, especially the souvenir shops. It is a sad that Cubans who do not have any US dollars are unable to buy anything from these US-dollar places even if they have the equivalent of Cuban Pesos.
What is interesting to me are the true-blue Cuban-Peso Department Stores. They are in large dingy halls with show-cases. One third of the glass displays were perhaps broken. Some of the remaining ones were held together by duct tapes.
These were lined with some clothes, the odd underwear, casettes, some parts of the pipings, glorious glorious plastic flowers and the most horrible-looking mass-produced porcelain ceramic statues in the world. A section had ancient, tattered, revolution-themed, multiple-hand books.
Booze and cigarettes are freely available - otherwise there's no bread, no butter, no basic necessities. If you don't get fed by your hosts or hotel then you're in trouble. Of course there are El Rapido places a la McDonald but somehow everything tastes there as if deeply fried in motor oil. So what to eat if you are on a budget ? Have rice with beans with your hosts :)
Went into a supermarket,it wasn't stocked very well but had the basics.
What to buy: Bought some Havana rum, the bill was lass than 5cuc's.
What to pay: less than 5cuc's.