Sometimes we Android Developers may be using a mobile broadband connection and one of the problems with that is the connection is not always that stable.
As you know the Android SDK manager does not resume downloads. The trick is to understand that you can use some know-how and wget -c to get it done. If you view the cache in your android meta hidden folder at your computer user root folder you will notice the dl-ssl.google.com url.
That is not the base url to use, its dl.google.com/android./repository at least for the android Google stuff to download. The 3rd party downloads have the right download base url as the last url line in the individual item descriptions in the xml files.
Works real well, as I have downloaded stuff while at an eating place that provides wifi. Once downloaded you than unzip it and place it in the right place in the SDK.