The circuit only used two active components, this makes repairs easy for faults caused by two common power supply mistakes (reversed current, or excessive voltage). Most of the other components aren't that sensitive to those issues.
IC1 is an ordinary low-cost audio op-amp. Although my original schematic diagram indicated a 741, that's only because the drawing program offered no other choices. The 741 is a terrible op-amp, it's very noisy. Out of the various op-amps I can buy from the local store (e.g. TL071, NE5534, etc), the best one has been the NE5534A (the “A” suffix indicates a version of the IC that's intended for audio use). Because it's a single-stage high-gain circuit (mike level to line level), you really want to choose a low noise, and stable IC.
IC2 is an ordinary low-cost audio power-amp. It's only driving headphones, so high power is not required. In fact, since the circuit is supplied over long cabling, low power consumption is desirable. I used the very common LM386 IC.
There's no special requirements for the resistors. None of them carry any high voltages or significant current. Many of the values were picked using trial and error from my stash of spare parts. I have used 1% tolerance resistors, since it makes things more consistent between several intercom stations (e.g. they'll all have the same gain).
Again, there's no special requirements for the capacitors, other than to be careful to observe the correct polarity. You may want to use non-polarised caps for the connection from the volume pot to the intercom bus, but there should be next to no DC there, anyway.