What's good for beginners?

Swimming or water aerobics would be excellent if you have access to a pool.
Beginner yoga is probably good, too. I have an iPhone app called All In Yoga (I think) and it allows me to set up short programs of a few specific moves.

Also, with regard to walking, if you have an outdoor destination you can walk to, it might help to feel like you are actually getting somewhere. I walk to the grocery store and home again, or to the smoothie place, etc.

Swimming and water aerobics are great full body exercises that don't put a lot of stress on your joints. You could also try the elliptical which will let you go faster than walking, but not put too much strain on your knees. Strength training to build up muscle is also a good idea.

Walking has been the mainstay of my weight loss - all I really did for the first 5months or more and I lost a heap of weight doing it. Do it often and as fast as you can and it will make a difference- guaranteed!

I started about 90 days ago and could hardly do 2 minutes on the elliptical at the gym. Now I am doing 30 minutes of elliptical at level 11 and 30 minutes of strength training each day. I still can't do any of the preset programs on the elliptical as they are too hard for me. I have artificial hips and can't run and walking hurts. The elliptical doesn't bother my legs I just had to be patient for my ability to extend my time.
I am also starting to add in some yoga for core and flexibility.
During the summer going to the lake has allowed me to get a lot of swimming in and really spikes a weight loss but now that winter is coming I won't have that.

I lost about 275 lbs in total over the course of 2 1/2 years, and did so primarily with just walking. Once I gained the endurance, speed walking. That and keeping your calories in weight loss range (just calories, for large weight loss don't worry about the macronutrients) will lead to large, fairly quick weight loss

I need to lose 150+ and I'm just starting out, what's good besides walking? Dr says no running yet love to walk but just doesn't seem to be going anywhere fast.

What do you mean by "doesn't seem to be going anywhere fast"? If you mean weight loss, it's 90% diet. If you mean it doesn't feel challenging, add in hills/stairs. Walking is great. It's all I did for my first 6 months when I started.

Every time you walk, you are achieving success;however, you may not be able to see the results on the scale immediately. Enjoy this journey, it will take awhile. When I'm not walking outside with a friend, I enjoy the treadmill or elliptical at the gym. I also have severeal of the Leslie Sansone Walk at Home DVD's......these provide variety and helped motivate me in the beginning.

I need to lose 150+ and I'm just starting out, what's good besides walking? Dr says no running yet love to walk but just doesn't seem to be going anywhere fast.

Walking is great for you. have you got access to the gym running machines?? If so put them on an incline you can burn lots of calories on these machines. My pic is a walking session on one set at it's highest level and walking as fast as I can.

Take it easy and build yourself up. doing challenges Quickest mile, improving on your time stops you getting bored. Elliptical Trainer is also good and a bit easier on the joints too!

Any decent gym will help you set up a circuit.

Enjoy it though don't look at it as a chore!

swimming, water aerobics, walking, and weightlifting.

If you love walking, that's great! You just have to think of ways to keep changing it up (both physically and mentally). Walking to a destination is good, but also adding in some difficulty (do you have hiking options where you live? hills?). You can actually lose a lot of weight through walking and a good diet.

If you decide you want something besides walking, I second the recommendations for swimming and cycling. They are both low-impact and can help you get into shape without beating up your bones and joints.

(Running's awesome too but most people need to work up to that!)

Also, I always tell people to find activities that are FUN. If there is something you've always wanted to try, or something that looks like it would be fun, try it! That could be yoga, zumba, kickboxing, hiking, mountain biking, water sports, mountain sports, climbing... you name it. If it's fun then you'll do it more, which means you'll get more skilled and more fit.

If you're walking, even to a destination, make sure to listen to upbeat music while you're walking. It makes the walk less boring!