Yes, take a look at Men's Health Magazine this month. There are some very good golf-related exercises in that magazine. Many other worthwhile tips guys can appreciate as well. Magazine is well worth the money.
I have tried those exercises mentioned in Men's Health. Very good.
For lower back, alternating Supermans is a good and simple exercise to do at home. You lie on your stomach, with your legs and arms outstretched (get as tall as possible). Lift your left arm and right leg off the ground at the same time. Return, then do the same with right arm and left leg.
For abs, most types of crunches (try crunches with knees dropped to either side to work the obliques) and leg lifts are good and simple.
One very important thing to note is that flexibility may be even more important than strength when it comes to golf swings. Do exercises to stretch the abs/waist/lower back. One good exercise is to sit on the floor with legs outstretched. Cross over your left foot over your right knee. Slowly twist yourself to your right, using your left elbow against your left knee as a brace, until you feel the stretch. Your right hand will be on the floor behind you. Hold for 15-20 seconds. Repeat on the other side.
Another good trunk stretch is to lie on your back, with your arms out to the side. Lift one knee and cross the leg over the other leg, twisting your waist to do so. Your shoulder blades should remain on the floor. Hold for 15-20 seconds as you feel the stretch. Repeat with other leg.
Remember with both of these to GO SLOW!