Continue a class discussion when you run out of time.
Have students generate ideas on a topic or on a reading that you will address in class.
Build community by creating an informal discussion space where students can raise questions and exchange thoughts throughout the semester, "Rants, Rambles and Responses" (or whatever you'd like to call it).
Ask students to post their writing to a discussion forum and have other students read and reply to it. (This usually works best when each student reads the entry above and below their own, so everyone receives feedback.)