Can anyone suggest ways to help me improve my left hand on piano/keyboard?

(Note: I will be referring to piano although I primarily play on a keyboard, but I wish to develop my piano playing skills).

I have noticed that my left hand is rather poorly developed when I try to learn and compose music. I can’t seem to steer far away from simple chords or slow scales whilst playing in time with my right hand. I partially blame my first few keyboard teachers – as I was playing on a keyboard and was instructed on using the stupid styles and one/two finger chords which hasn’t helped me to develop much flexibility in my left hand.

So does anyone know any exercises, recommend any sites/books, or have any tips to help me develop my left hand preferably whilst playing with my right hand as well. Also can anyone recommend any cool numbering to use on the left hand that beats the boring 1, 5, 8, 5 and 1, 3, 5, 3.

Thanks a lot