A third "Ghostbusters" movie is said to be in the works, according to Variety.

Columbia Pictures wants to reunite the original cast members and has set Lee Eisenberg and Gene Stupnitsky to write the script.

Previous efforts to make the third sequel have been stalled by failure to come to financial terms with the participants, Variety writes, and the original cast members have not been approach until the script is ready.

Update 9/8/2008:
Chicago Tribune's Pop Machine blog got a statement from Harold Ramis.

"yes, columbia is developing a script for GB3 with my year one writing partners, gene stupnitsky and lee eisenberg ... aykroyd, ivan reitman and i are consulting at this point, and according to dan, bill murray is willing to be involved on some level."