Carbonfiberboy 

Leg extensions are contraindicated. All else looks good, except that you're not hitting your legs or core enough. Since you're doing leg extensions, you must be using a gym. Add a session on a back machine, leg sled, squats, and maybe a sit-up bench. I like this order: sled, rows, back, squats, push ups or benches, one-legged calf raises, abs, pull-downs. You can mix and match to suit.

The much more complicated question on this thread is how to add weights to your regimen. I'm going to ignore track sprinter training here. That's a very small number of cyclists and a very specialized discipline. For the average rider, racer, TTer, etc., there is no benefit to be found in conventional weight lifting over using the same time to ride. That's been shown by a number of studies, and there are no studies showing the opposite that I know of. My metric here is a reduction in 40k TT times, which roughly translates to increasing power output at LT, which is how you beat your buddy on the weekly hammerfest ride. By conventional weight lifting, I mean the usual 4-12 rep stuff, starting with 12 for hypertrophy, and gradually decreasing to 4-5 reps for maximum strength over a period of weeks. Doing any sort of intervals instead of using that time for lifting always beats lifting all hollow.

It is true that conventional weight lifting increases the amount you can lift, which is a form of strength, and increases muscle mass. However, "strength" on a bicycle is measured differently. You will hear TdF commentators say that the strongest man will win. They don't mean the rider who can squat or deadlift the most. In fact it might even be the inverse of that. Winning stage racers have to shed a lot of protein.

All that said, I think there is a place for weight lifting in one's training regimen. Weight lifting increases resistance to injury. It increases muscle mass, which may or may not be a good thing, depending on the rider. It increases sprinting power, which is often useful. In winter climates inhospitable to cycling, it's something different to do.

The first thing one needs to consider is that no single element of a training program can be considered in isolation. Weight lifting adds a great deal of training stress. It reduces the amount of energy a rider has for cycling. Since we are trying to get better at cycling, not weight lifting, lifting instead of cycling is contraindicated. Since we know intervals increases a cyclist's power more than weight lifting, if we are doing weights instead of intervals, we have hold of the wrong end of the stick. But we don't do intervals all year. Most riders who are training seriously devote the winter to base training, using intervals sparingly and at lower intensities than they will in spring and summer. So this is the period when you want to work on the weights, if you are so inclined.

My rule is that I try not to allow weight training to take time away from bike training. So this has to do with how much time one has available for training, and how fast one recovers. Each person is going to be different. Some will be able to ride in the morning and weight train in the afternoon. Others will only have evenings available, which is my situation. I only lift after I ride because my focus is on improving my riding so I want to ride when I'm fresh. Also, one wins sprints at the end of a ride, not at the beginning, so it makes sense to weight train after the legs are already a little tired from riding. I also want some days off, so I certainly don't want to add training stress by lifting on a day off. I find that my lifting is not greatly compromised by riding first, though it may be until one gets used to it. The two disciplines involve different energy systems and different fiber recruitment.

I find the greatest benefit from doing about 30 reps (for non-body weight exercises) circuit style and from doing them almost to failure. IOW, the last few reps should be very hard. From time to time I will use enough weight to achieve failure, IOW not quite able to do the 30th rep. This must be done judiciously or you will compromise the next few cycling workouts. If you recover well, you should consider doing two or three circuits, all at the same weight, once you can do one circuit and have energy left over. Each circuit should take no more than 20-30 minutes. As your conditioning gets better and your connective tissue gets stronger, you should increase the speed of your reps as much as you can without bouncing the weights. This regimen will increase muscle mass and cycling-specific strength, there's no question.

When you start to add hard interval training in the spring, taper off the weight training, going down to just once/week, then down to fewer reps at the same weight as 30, then stopping the weight training completely. This is the time to shed excess protein that was added by weight lifting, along with that winter fat.