- MuseScore: MuseScore is a community of musicians who share and collaborate on sheet music. You can find a variety of Super Mario sheet music on MuseScore, including arrangements for piano, guitar, and other instruments.
- The Super Mario Bros. Music Archive: The Super Mario Bros. Music Archive is a website dedicated to preserving and sharing the music from the Super Mario Bros. games. You can find sheet music for many of the songs from the series, including the main theme, the underground theme, and the castle theme.
- Ninsheetmusic: Ninsheetmusic is a website that provides free sheet music for Nintendo games. You can find sheet music for many of the Super Mario Bros. games, as well as other Nintendo games such as Zelda and Pokémon.
In addition to these websites, you can also find free Super Mario sheet music by doing a Google search. Be sure to use the filetype:pdf search operator to only return results that are in PDF format.