As others noted, there's a sequel film 2010. Both 2001 and 2010 are also novelized, and there are five additional books: 2061 and 3001 are "far in the future" sequels following some of the same characters (and the monoliths).
There are also three other novels under "A Time Odyssey". Separate story but with similarities <spoiler>mysterious outsiders and fascinating human-made AIs</spoiler.
There are also three other novels under "A Time Odyssey". Separate story but with similarities <spoiler>mysterious outsiders and fascinating human-made AIs</spoiler.