A few people have asked me what training I did for my century ride.
I'm currently riding 4 days a week (well, I took 10 days off at JavaOne and on vacation). Monday/Wednesday/Friday, I do a 15 mile ride which takes about an hour. It has some up and down hills, and a steady 2.5 mile hill in the middle. I try to ride that hill at a somewhat painful steady-state, where my legs are hurting but I don't feel like I'm going to die.
On the weekend (usually Saturday), I'll go on a long ride. I started at around 30 miles in March, progressed to 50 miles in May, and then peaked at 70 miles the week before the century. I aim for a pace that will leave me tired at the end but not so I couldn't ride more if I had to, which obviously varies based upon the distance.
For the century, I found it to be hugely useful that I had ridden the bulk of the course before, so that I knew where all the hills were and how steep they were.
I'm planning on adding more mileage as the summer progresses, and perhaps a new bicycle.
Oh, and I haven't yet gotten around to getting a heart rate monitor yet, though that would probably be a useful addition. I bought Chris Carmichael's book a while back, and I'm planning on trying some of his training drills - I would really like to be able to bump my average speed up a few miles per hour.