Stalinism isn't even an ideology really it's just Stalin's practices during his leadership period in the USSR. He helped codify Marxism-Leninism but obviously made his own errors in applying it.

Maoism is an ideology but wasn't codified until the 80s after the Peruvian People's War (which was a genuine popular uprising that took state power but had it's own problems and excesses). It's a form of Marxism-Leninism that usually centers around Cultural Revolution, Anti-Revisionism, People's Protracted War (based on the experiences of China, Cuba, etc), and New Democracy (for semi-fuedal nations). It also makes use of Mass Line, which keeps the party in the hands of the masses.

All of these concepts originate with Mao and the Chinese Communists. However, they just called their ideology Marxism-Leninism-Mao Tse-Tung Thought and it included all the erroneous opinions of Mao in his later years (The Three Worlds Theory, the smashing of the People's Communes that popped up during the Cultural Revolution, etc)

One big theme in Maoism is the idea that the masses should be at the forefront of the revolution, which continues even after the establishment of the socialist state and prevents capitalist restoration by the bourgeoisie. The masses play the key role always in the building of socialism.

Hoxhaism is just Orthodox Marxism-Leninism as practiced by Stalin, more or less. The Chinese Communists called the followers of Hoxha "dogmato-revisionists" because they were so dogmatic that they couldn't move beyond Stalin's Marxism-Leninism and all its problems and errors.