The St. Louis Argus launched its online forums yesterday. Antonio French, the paper's news editor, calls the Argus "St. Louis' true alt-weekly."
Speaking of online forums, the best ones in St. Louis are at readjulia.com. They're very active and populated by smart, funny people (unlike the trolls that hang out on the STLtoday boards). Julia's forums manage to be cozy without being xenophobic.