The first useful breakfast cereal I found post dietary changes was Cheerios. After that came Fiber One, which uses a little artificial sweetener to mask the addition of fiber in their product. After a while, too much Fiber One and you can feel as if you’re eating sawdust.
Nature’s Path has a good multibran cereal that I use sometimes. This new cereal is also pretty good. Not my find, my wife dug it out on a trip to Whole Foods.