If you allow computer games and he likes that (thinking on the ADHD as we have a son unofficially DXed with it as well), there might be some help there. There are many free sites that allow for drilling of multiplication facts.’
http://fun4thebrain.com/mult.html
http://www.arcademicskillbuilders.com/ (they have a whole tab for multiplication)
Does your son know the patterns and see them? I have a resource I created for my son, and he could really SEE it then. I could send you a link if you wanted via PM. I don’t want to link here as it is an external site. Not sure about the rules on that.
I also have several pins on my pinterest board with visual games you can do.
http://pinterest.com/ldimom/math-ideas/
If your son likes card games, you might check out this link as well:
http://letsplaymath.net/2006/12/29/the-game-that-is-worth-1000-worksheets/
This site has lots of ideas: http://www.livingmath.net/Home/tabid/250/language/en-US/Default.aspx
Also, this game is on my wish list, and I’ve heard lots of great reviews:
http://www.amazon.com/Speed/dp/B005E8W36C/ref=sr_1_1?ie=UTF8&qid=1358547054&sr=8-1&keywords=speed+game
HTH