Grand Central Dispatch (GCD)

// Doing something on the main thread

dispatch_queue_t myQueue = dispatch_queue_create("My Queue",NULL);
dispatch_async(myQueue, ^{
    // Perform long running process

    dispatch_async(dispatch_get_main_queue(), ^{
        // Update the UI

    });
}); 

If you want to run a single independent queued operation and you're not concerned with other concurrent operations, you can use the global concurrent queue:

dispatch_queue_t globalConcurrentQueue =
dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)