How to wire Two dimmers controlling a string of recessed light?
As @Tester101 says, with conventional dimmers, you can only have one dimmer in a circuit if the fixture (or set of fixtures) is being controlled from more than one location. 

If you are switching from two locations, you also need to use 3-way switches for both the plain switches and dimmers (many dimmers are 3-way compatible). 

There are specialized dimmers that work as master and slave units. These do allow dimming from multiple locations, but you need to use a set of matched units. These are also much more costly than basic 3-way dimmers.

Finally, if you are running remote switches that only connect back to the first set of switches, you need x/4 cable, not x/3. Two wires serve as travelers, one as the common return and one as neutral.  While not every switch requires a neutral, code now requires it as a hedge against future active devices. If you do not need the neutral, simply cap it in the box.