Long Distance Competition/Ultracycling, Randonneuring and Endurance Cycling - List of Centuries?

I'm looking for a century to prepare for...

...Most of them that I can find or already know about seem to be in the next month or two and that's a little close for me I think. I'd like to make sure that I'll be in shape for it. Then keep doing them as much as possible.

So does anyone know of a site that lists centuries by area/date?

Well, it depends on where you live. Google randonneurs and your state. You'll come up with a name or list of names of bicycle groups in your state. Click on one and check their ride calender for the year and look for any rides around the time that you like and the distance that you like. You will almost certainly have to be a member of the group to ride with them and they'll keep track of your miles for the year.
You click on the link for the contact person next to the desired ride and let him/her know that you want to register for that ride on that date. There may also be a link for a map or cue sheet so you can look over the route ahead of time and see it you like it.
For instance the Lone Star Randonneurs (http://www.lonestarrandon.org/) have a few rides still coming up for this year and the president of the group is already preparing the calender for 2010. Hope this answers you question.
Ernest

You might check Raceplace or other event magazines that are at your LBS for cycling events.

I know of a couple of sites, but they're both regional, one being "Texas", one being "North Texas".

Look up some of the cycling clubs and some of the larger bike stores in the general area. Some of them will have a list of centuries.

Things drop off a lot as you move out of summer, so there may not be much to choose from later in the year. One thing that happens is that you can have nice weather, but it's a lot more iffy, so makes it harder on the ride organizers.

There used to be a site that had a list of centuries called Bike Centuries or something like that ... but the guy who created it, created it, and almost immediately stopped maintaining it, and it's gone.

However, you might be able to find something that appeals to you from my Links page:
http://www.machka.net/links.htm

Check out active.com and bikereg.com. Both sites let you search by region/state/zip code, and for many events they'll provide online registration.

This site has an excellent of centuries and other long rides on the west coast, with a special emphasis on the Pacific Northwest:

http://www.bikingbis.com/blog/_WebPages/BicycleAdventureIndex.html

It also has a very long list of all of the "multi-day" rides (like RAGBRAI, Cycle Across Oregon, etc.).

And it's a good blog in general..