ADHD is a very "hip" thing with doctors and educators right now, and I'd look at it with a grain of salt the size of Utah. Many people call ADHD not a learning disability, but a teaching disability. These kids are usually massively bright, iconoclastic, self-motivated, and quick to learn if taught by intelligent people. They're not "easy" kids, but they usually make the best adults.
Check into the dietary modifying book by Dr. Feingold--I think it's called "The Feingold Diet." He links hyperactivity and learning disorders to diets high in additives and salicylates. That sometimes helps. Check into the book called "The Gift of Dyslexia" (also covers ADHD) by Ron Davis. Davis is a self-healed autistic and dyslexic who discovered why the smartest people among us often have the hardest time learning. That book rocks. Both will give you a much better picture of the situation than someone who wants to push Ritalin ever could.
With my O son, keeping him off wheat and corn was a giant factor--also knocking out any avoids, and making sure he had enough meat in his diet (organic, of course). And of course, a daily B-complex is a must. But, further than that, I saw that he was miserable in school--that they were teaching him stuff that had no meaning--and that being around too many other kids all day made him exhausted. We think that school is a natural thing--something that kids just have to get used to. But it's not.
So, I took him out and home-schooled him. Surprise! At home, he's got no ADHD at all. He's just a bright, iconoclastic individual human being who needs to be treated as an unrepeatable person, and not as one of 30 kids in some class run by some overwrought and underpaid guy. The homeschooling was no big deal. There are tons of books (John Holt's books on "unschooling" are the very best. See "Teach Your Own" by John Holt).
Homeschooling clearly doesn't work for every child--many of them like the social atmosphere at school. But my son hated it--he's a very solitary guy--and he jacked up his energy at school just to make it through the day.
Now, he's 17 and graduated from high school (kids can test out at 16 in California), and he's planning to become a theoretical physicist--we're looking at Berkeley and MIT. He's learned to marshall and manage his own energy without drugs, and he's fine. It's cool.
I myself was hyperactive as a child, and my mother--God bless her every day--said a strong NO to the Ritalin that was being pushed at me. She felt that if I had that much energy, I must need it, and that I should learn to work with it drug-free. She was right in the long run, though it was hard to go through school with so much energy. Now, though, I can do more things than anyone I know--so it has become a great gift.
If you look at hyperactivity as a disease, you'll make decisions based on a broken child model. But if you look at it as your child's personal response to the world, you'll be able to make decisions that value and honor his soul, rather than valuing and honoring the makers of Ritalin.