Any good sites that explain workouts, how to do them, etc.
There are lots of them. Like anything some good some bad.
As WW says, you need to first define your objective.
Are you working out to lose weight, get fit, gain mass?
Do you have target areas or are you looking to improve your entire body?
What kind of equipment or facilities do you have access to? For example i work out alone, in a gym I have set up in a storage area at my office. Thus my work out involves a lot of strength exercises where I don't even use weights such as pull ups, push ups, balance and core work along with free weights.
While videos are great my opinion would be for you to hire a reputable trainer. They can give you excellent advice on proper exercises for you, proper form (essential for gains and to reduce risk of injury) and most importantly nutrition and rest. You can work out like a freakin' mad man but if you don't rest and eat properly your gains will be shit. After a while you can back off from the trainer and run with what they have given you but go back occasionally for a tune up and to change up your routine. It is important to have a bunch of exercises for each muscle group and rotate them. That is again where a reputable trainer can help. If you are doing arms, do not do the same arm exercises each work out. Muscles need to be challenged and sometimes just changing the angle of your arm curl for example makes a huge difference.
Don't forget your legs. Too many guys especially, concentrate their work out on their upper body and not the legs. We've all seen them in the gym. Huge arms and skinny little legs.
Also legs are very important if you are trying to lose weight. They are your biggest muscles and the largest consumers of energy. If you work your legs hard they significantly increase your body's energy demands while they repair and grow (again while you are sleeping). This will help you to burn fat if that is your objective. Leg work gives you a six pack.
You want nice abs? Don't waste time with sit ups. Do core exercises, cardio and leg work.
Hope this helps.
J