Yes there is no incorporated software to use microphone in Kindle Touch but that doesn't mean we can't use it!
I wrote a very simple audio recorder and player. It might help in case you want to record something and you don't have your cellphone handy! Well this has more applications ...
O start recording
 stop recording
> start playback
|| stop playback
- GUI Launcher
0. Do you have SSH access to your Kindle?! If not, read this: USBNetwork
1. extract zip file to /mnt/us/
2. execute 'restart framework' through SSH
3. Guess what? -> Done!
Karma and happiness to all of you wonderfulz!