What is the best way to watch the Vuelta?
Comcast dropped Universal Sports. Universal's website no longer offers a subscription streaming option. You can stream from the website if you are a Dish or DirectTV subscriber. I am not, though I could drop my Comcast sports package and get a Dish subscription.
Others mentioned some good options, but to my knowledge neither of them have archived streaming available. If you're like most of us and work during the times when the live races are on, it's difficult to follow them. Cycling.tv offers archived coverage of most major races, so you may want to check them out. They are subscription, though.
I'm betting Universal Sports will realize they made the dumbest move ever once the Olympics are over and start offering pay packages again. After all, some revenue is better than no revenue and no revenue's exactly what they're getting from the millions of people that are subscription video customers but don't have DirecTV.