Have a look at Bill Pearl's book "Getting Stronger". He has cycling specific workouts, one for in-season, one for off-season. I can't comment on their effectiveness though, as I'm just commencing the off-season one myself.
went through the same thing myself a year ago. Couple of thoughts, first, cross training works great. Start with an *easy* schedule, say 3 times a week. My easy schedule is like this, Tuesday-easy aerobics and weight training for legs and back. Thursday is moderate aerobics and arms/stomach. Saturday is for riding or a spin class in winter, or hiking. Limit yourself to 30-35 minutes in the gym to start. Allow a couple extra minutes every week or two.
Now, here's the bit that will really knock your socks off. Get 'The Heart Rate Monitor Book for Outdoor and Indoor Cyclists' by Sally Edwards and Sally Reed. There is a logbook you need to get with it. This is the best training aid I have ever seen. You'll need a heart monitor, but
a cheap Polar will do the trick (you can even find them used on the internet)
Definitley start with an easy schedule. Dont over do it the first week or two. I over worked myself after a 6 month haitus, i passed out on the sidewalk. I woke up 5 mins later. Thank god, no one stole my bike.
Id say start off easy with 30 mins every other day. I just biked 30 mins everyday and upperbody work outs( situps, crunches, etc, etc). Not to mention dieting. THIS IS VERY IMPORTANT!!! Why excercise if you are going to down chicken wings.
I worked my way up to 1-2 hrs of biking every day (depending on the weather) lots of upperbody workouts (200 situps, crunches, and 100 pushups) I cut carbs to a mininum, no fats, fry foods, sugars or fast food. Lots and lots of fruit. Whenever i get hungry, i eat several pieces of fruit. 3 months later, im down 25lbs, with more muscle, and less 4 waist sizes.