I have done flash cards, but we all get bored with them. The favorite drill methods at our house (kids and my opinion) the first two being what we use the most:
Math Wrap-Ups – you can get individual sets, but I bought the whole thing
Schoolhouse Rock videos – I have this DVD, but I have heard they are free on Youtube I think, and when I looked they are free on Amazon Prime
various free iPad apps I’ve downloaded – Rocket Math comes to mind as a favorite
someone mentioned these songs I intend to check out – Math Songs at havefunteaching.com