I want to be fit to do some hiking this coming summer. Are there any online workouts that will improve my physical condition and make hiking easier? I will be hiking with a 20 lb. pack then.

Coming from someone who has done many conditioning hikes with 60+lb packs (military) here is some advice.

This first thing has nothing to do with fitness. Don't over-dress. If it's cold outside don't go wearing a coat on a hiking trip. (bring one) but don't wear it. Wearing one can cause over-heating.

Secondly, hiking isn't all about legs. Work on your back as well. 20lbs isn't a lot but after 25k it feels like a ton.

Third (would I say thirdly?) Make sure to hydrate. HYDRATE, HYDRATE HYDRATE. Before, after and during (even if it's freezing cold out)

Fourth, hiking takes a lot of stamina. If you're a smoker you will need to work on your conditioning more so then a non-smoker as you will get winded a lot quicker.

Lastly, when I hiked I was always holding a weapon (not sure if you will hold anything) but arms get tired after hiking/walking too.

To sum it up. Dress appropriate, drink water, work on legs, back, arms and conditioning.

P.S. Stretch. I almost forgot stretch, stretch, stretch!

Thank you for the answer... altho I'm kind of looking for a program to follow...

Well I am unsure of specific program but if you know what areas you need to concentrate on Google is your friend!