Originally Posted by Carbonfiberboy

One-legged pedaling is good. I have a lazier leg so I do it religiously for a few months each year, on my rollers. Trainer is fine, too. I use a system of intervals like this:
Each leg for 2 minutes, 50-55 cadence.
2 minutes legs together, moderate effort
Each leg for 2 minutes, 80-85 cadence
2 minutes legs together, moderate pace.
Repeat until exhausted. The chain must never go slack. Use a gear that allows you to keep a taut chain all the way around. When it starts to go slack, the leg is done for that interval. You probably won't be able to manage 2 minutes to start with. Do what you can and still keep a taut chain. It'll gradually get better over a period of months. I can keep doing those intervals for up to 45 minutes, but I've been doing this for many years.

Another good way to strengthen a leg is doing one-legged leg presses and one-legged leg extensions at the gym. You can also do one-legged knee bends on a chair with one hand on the wall. Do 3 sets of however many you can.