Maelstrom is an excellent Asteroids-type game with sound and 3D objects. It is fantastic for casual playing, it plays over a network and has excellent graphics. It compiles easily under both Linux and Solaris and there are binaries for several UNIXs available.
SDL is a library that allows you portable
low-level access to a video framebuffer, audio
output, mouse, and keyboard. With SDL, it is easy
to write portable games which run on many
SDL_mixer is a simple multi-channel audio mixer. It supports 8 channels of 16 bit stereo audio, plus a single channel of music, mixed by the popular MikMod MOD, Timidity MIDI, Ogg Vorbis, and SMPEG MP3 libraries.
splitvt takes any VT100 terminal window and splits it vertically into two shell windows. It allows you to watch two terminal sessions at once, which can be very useful whenever you want more screen real-estate without messing with windows.