If you wondered where all those unwanted statues of Lenin ended up, you'll find some here, along with the red star from atop Sofia's Party House. There's a gallery of paintings, where you'll rejoice in catchy titles such as Youth Meeting at Kilifarevo Village to Send Worker-Peasant Delegation to the USSR, and stirring old propaganda films are shown.
The museum isn't the easiest place to find. Catch the metro to the GM Dimitrov station, in the Iztok suburb; walk north up bul Tsankov and then turn right onto ul Lachezar Stanchev. The museum is housed in a gated Ministry of Culture building next to the Sopharma Business Towers. You can see the big red star in the garden.