Many a times it happens that you lose some good offers specially the free one for your Xbox because you are at work and going home is not going to be any time soon. Though sad but if you have access to internet you have a reason to cheer up.
Your Xbox live account ( Gold or not ) allows you to schedule and start download to your Xbox console right from any where. All you need is to signin to your Xbox account at xbox.com. Once you add downloads to the queue, it will start automatically in your Xbox if it is turned on else when it does.
For every downloadable content you will see a green button which says, Download to Xbox 360. This will start the download to the your registered Xbox console.
To see all your downloads, check the queue and your download history. From here you can add any content which you have bought before. Though I am not sure but it would have been great if my web account was able to check and let me know if I already have the content in place when my Xbox is turned on.
Also if you want to stop download, you can remove it from queue. Once your content is download you will see status as complete here. So if your Xbox can stay connected to internet all the time at home , you will not miss any offer.