[calloc]

You can still insert a barrel jack, this time with 4 rings instead of 3 at which point the microphone is disabled.

For example, Apple headphones for your iPhone can be plugged in and used for that purpose...

[pavel_lishin]

Only if you cut the microphone off, of course. :)

[stcredzero]

You can buy a 4 ring 1/8" plug adaptor for headphones. Some of these adaptors come with no mic.