Board to board communication (Backplane) in possible noisy environment- UART, RS232, RS422, RS485?
For medium and low speed signals (UART, I2C, etc.), the direct approach of using logic-level signals is usually fine. You just need to make sure that the signals being driven onto the backplane have sufficient drive for the maximum anticipated load. Use buffers if necessary. You can add a ground plane to your backplane to help shield it, if the enclosure it's in isn't sufficient.

For high-speed signals (SPI, etc.), you can still use logic levels, but now the lines start to behave as transmission lines. You need to pay more attention to trace impedances, stray capacitance (particularly in connectors) and crosstalk.

For really high bandwidth, the trend is to use LVDS signalling; PCIe is one example of this.