Loren, dialogue is usually when ellipses are used since one of their purposes is to indicate a voice trailing off. The other is to indicate that you've omitted pieces and parts of what you are quoting.

Semicolons are frequently used in dialogue as they can be used to connect two related sentences or to break up certain types of series.

Gary posts on ADB's BBS; he doesn't post on Mongoose's forums.

Loren writes short stories, poems, and tactics papers; draws zombies and Star Fleet officers; and builds lovely wooden bookcases.