In terms of visitors and size, Frankfurt's Christmas market is one of the largest Christmas markets in Germany. There are creative stand decorations, scenic surroundings and wonderful German foods. Its something to enjoy if you are there.
This Spring Dippemess is the largest folk festival in the Rhine-Main region. There are markets and stalls as well as a folk fair with fairground attractions. You can find fun and games for the whole family there.
Wäldchestag means "Forest Day" in German, maybe because its from a different time, but everyone heads to Frankfurt's city forest to celebrate. The Wäldchestag is a symbol of how much the citizens of Frankfurt identify with and love their city. It is an important custom and part of Frankfurt's urban life. Its a national holiday where everyone enjoys the weather and has fun in the fairs and carnivals.
Rheingau Wine Festival is an annual wine festival that attracts wine enthusiasts from all over. If you enjoy sipping wine in general this is something you need to go to.