Connection of EZ430-RF2500 development tool with PIC18f877
You can connect the PIC's UART to the MSP430's UART directly, if the power supply voltages are the same.  So, it is possible get away without an RS-232 driver such as MAX232.  Of course, you would need to connect the grounds together.

As a side note, MAX232 generates the true RS-232 voltage levels.  These are higher than the voltage levels, which the UART outputs.  The benefit of higher voltage levels is that the true RS-232 is more immune to interference.

What if the power supply voltages aren't the same?

PIC16F877 can use supply voltages between +2V and +5.5V.  MSP430F2274 on the ez430 can use supply voltages between +1.8V to +3.6V.  Suppose that the MSP430 runs off +3.3v, and the PIC runs off +5V.  MSP430F2274 doesn't have inputs that are 5V-tolerant.

The supply voltage ranges overlap.  May be, lowering the supply of the PIC16F877 to +3.3V is an option.  You may need to lower the oscillator frequency.  Check that other components, which share the power supply rail with the PIC can operate off +3.3V.

If your design doesn't allow you to lower the PIC's supply voltage from +5V to +3.3V, there are level shifters (or level translator) ICs.  See this post for details.