Nonblocking sleep in C#5.0 (like setTimeout in JavaScript)

AsyncCTP has TaskEx.Delay. This wraps timers in your task. Note, that this is not production-ready code. TaskEx will be merged into Task when C# 5 arrives.

private static async Task ReturnItAsync(string it, Action<string> callback)
{
    await TaskEx.Delay(1000);
    callback(it);
}

Or if you want to return it:

private static async Task<string> ReturnItAsync(string it, Func<string, string> callback)
{
    await TaskEx.Delay(1000);
    return callback(it);
}