The next World Wide Flash Mob (number 10) is scheduled to take place on May 4th, and there is sure to be one near you. But how can you find one? Well, you can do a search on geocaching.com for all caches with WWFM in the "cache name" (I leave off the "X" in the name, because different event hosts use different variations, which may limit your search results).
This search produces a list of 270 events (as of today), but unfortunately, you can not sort by location, making it difficult to find any in your neighborhood.
You can use the Podcacher's List, by State, but while it's nice to see the number of events planned for each state, there's still no easy way to see just the WWFMX's planned for your state.
The best thing I've found to do is generate a pocket query in which, under "Selected Types", you only select "Event"; and under "Placed During", you select May 4, 2013 as both the begin and end date. Then, just select your "Radius" within your "home location". You'll get all the events planned for that day near your home - and they will all likely be WWFMX events.
Save your query, then go to the Your Pocket Queries page and select the "Preview in Geocaching Maps" icon; and there you have it:
May the 4th be with you, and Cache On!