My old Nokia had a 2.5mm headphone/microphone port. I've recently had that phone stolen and moved to a EVO 3D. It has a 3.5mm port: however, is this a compact headphone/microphone or just stereo headphone?
It is a headset (as opposed to merely headphone) port, tested using TRRS (tip ring ring sleeve) Klipsch Image S4i headset. Also, because of the peculiarities of the way HTC soldered the fm radio on the 3D, it apparently (I didn't test this, don't have any TRS headsets/don't care about FM) only works correctly with a TRRS cable.
You'll note on android, when you plugin a TRRS headset, the icon in the notification area is subtly different (it has a Mic boom under the headphones). If the notification area icon only has the 'phones and no mic, you probably don't have the headset plugged in all the way (happened to me with a case skin on my DInc) and music will sound kind of funny.