If you have an iPhone, look up the 7 minute workout app (it's free). It's basically 12 high intensity exercises, 30 seconds each with 10 second rest periods in-between. Like you, I'm close to plus size and and just started this ap about a week ago. It kicked my butt the first few days but it's getting easier and you can modify it (I do girl push-ups instead of regular push-ups). I also started doing planks on my knees instead of my toes, but I'm almost to the point where I can do it on my toes exclusively.
I really like it because it's not a huge time commitment and it's a good start to my exercise routine. Plus, you can do it in the privacy of your own home. I've been doing it twice a day and I push myself to do each exercise properly. I also plan on adding a few walks to my week and making better food choices. Good luck!
I have used Leslie Sansone in-home walking videos for the past two years with good results, lost 40 pounds so far. In my area, they can be rented from video stores or purchased at big box stores or online. She also has some free workouts on Youtube. I was skeptical at first, but being able to walk 1 to 5 miles in my living room when the snow is flying outside is great. Leslie is very encouraging, some people love that, and some don't, but it works for me. Another workout for us plus-size ladies is Debra Mazda. Her videos are great, too.