Njam is a full-featured cross-platform Pacman-like game that uses the SDL library. It features single and multiplayer modes (local or network), duel games where players compete against each other to get more points, cooperative games where players cooperate to finish as many levels as they can, and great music and sound effects. It includes customizable level skin, many different levels, and an integrated level editor.
While Performous might be classified as a karaoke program, it is actually much more than that. Instead of just displaying the lyrics, notes are also displayed, and the performance is scored based on how well you actually hit the notes. Unlike in many other games in this genre, you will also see the pitch that you are singing, so you can see what you are doing wrong and easily (well, everything is relative) correct your pitch.
pydance is a dancing game written in Python, formerly named pyDDR. The idea is simple. There's a floor mat with arrows, and the game scrolls arrows up the screen to the beat while playing a song. When the arrows reach the top of the screen (not sooner and not later), the player hits the corresponding arrow on the pad, and given that it's hit on time with the beat, points are scored. Based on how well the dance is put together, s/he is graded at the end of the song. Both keyboard and mat play are supported.