MongoDB drop every database

you can create a javascript loop that do the job and then execute it in the mongoconsole.

var dbs = db.getMongo().getDBNames()
for(var i in dbs){
    db = db.getMongo().getDB( dbs[i] );
    print( "dropping db " + db.getName() );
    db.dropDatabase();
}

save it to dropall.js and then execute:

mongo dropall.js