Riding Time and Cardio Workout

[Bluetree]

I also have time constraints, which has limited my workout time to a hour a day, except on Sundays. I think any workout can be a good one as long as you pay attention to your heart rate and push yourself, whether it be for speed or distance. I also think it important to mix up your workouts, and not stick to just one thing all the time.
My current WO schedule looks like this:

Tuesday: Bike 1 hour (work on speed and intensity)
Wednesday: Swim <1 hour
Thursday: Run <1 hour
Friday: Recovery day
Saturday: Bike 30-45 min.(easy) + short run
Sunday: Bike 2+ hours (work on time and distance)
Monday: Recovery day

Right now I am just building a foundation in all three disciplines, so I can start training in earnest next year. The guy who will be my coach told me that speed and distance figures mean nothing right now, except in relation to my own previous efforts. I think as long as you push yourself in whatever little time you have, it's a good thing.

[midgetcycler]

If you do intervals, that makes your short amount of time that much more efficient. Here is a workout in Self magazine this month. It can be applied to any sort of cardio you want.

40-minute workout:
Warm up for 5 minutes
Amp up to moderate (you can chat) for 5 minutes
Go easy for 5 minutes
Moderate for 20 minutes
Cool down for 5 minutes

If you are looking for something more difficult, try this 30 minute routine:
Warm up for 5 minutes
Increase speed for 5 minutes to about half your max
Speed up about 10% every 5 minutes for 15 minutes, doing the last 5 minute stretch at top speed
Cool down for 5 minutes

[Bad JuJu]

As others have said, whether you get a good cardio workout or not is all about your heart rate. Get your hands on a heart rate monitor (you can get cycle computers that include a heart rate function), find out what your HR zones are, and go to town!

[RoadRaven]

I have become very specific in my rides and basing each one around my heart rate and my cadence, followed by time on bike.

The distance is not as relevant now... my average speed is incidental in my training rides and the only time my speed is of interest is in a race situation.

A HR monitor is helping me be more effective and build my available power/strength on a bike, as well as helping with being in the right minimum zone to ensure every ride also counts towards a little weight loss.

I am finding big improvements in my riding basing my training on my heart rate - as JuJu says, get a HR monitor and go to town!