Here are some online resources for finding upcoming events and things to do in South Beach and Miami.
There are many annual events in the Miami area including the Miami Winter Music Conference, Ultra Music Festival, Miami Boat Show, and others. Here are some resources to help you find other, lesser-known Miami things to do:
Miami.com is produced by the Miami Herald and has a great events search feature.
Frommers has a useful guide to Miami events.
EventGuide.com has a section on Miami.
About.com has a monthly Miami calendar.