The schedule on the website reveals a huge number of spaces, places and genres of music where you can hear bands. Pick the one closest to you, pick the type of music you'll like best, or throw a dart to choose (but not at your computer screen!).
Take a look at the website for special events as well. The SecondLine New York caught my eye, as did the "Mass Appeal" project where you can show up with your own instrument and play in a band. Don't have an instrument? Find the pianos and play your own tune in "Play Me, I'm Yours".
And if punk is your thing, find your way to Governor's Island between 10AM and 5PM (Free ferries leave from Dumbo and downtown Manhattan) for Punk Island. You can guess what that is. A list of bands is on the website, as well as a reminder that no alcohol or weapons are allowed on Governor's Island. You can guess why that's there, too.
When: June 21, 2010 11AM-10PM
Where: All over the place in all 5 boroughs