I don't have many links for training because frankly I am not impressed with much of the information that I have found on ultracyclist training (I am sure that I have just not found good information yet). I have experimented on my own and I find that for me the best training is to work up to riding a century (100 miles) every day. Doing this while pushing the pace builds both endurace and speed. It also allows for a much faster recovery than if you go out and ride 200 or more miles in a day.
Please let me know of good training methods that have worked well for you.
Kurt Searvogel (his web site), Steven Abraham (his web site), and William Pruett are each making an attempt to beat Tommy Godwin's annual cycling mileage record of 75,065 miles set in 1939. The UltraMarathon Cycling Association (UMCA) is certifying the attempts. The rules and information about the current record can be found here. A spreadsheet with their mileage, which is updated daily, is here.