1/8" to 1/8" Male to Male connector. What's it for?

[OnlyBodyWeight]

What is the use for these?
http://www.ebay.com/itm/3FT-3-5mm-1-8-Male-to-Male-Stereo-Audio-Jack-Cable-for-iPod-MP3-MP4-DVD-Green-/290765541701?pt=US_Audio_Cables_Adapters&hash=item43b2fa1145
 
I am going to buy this so I can hook my phone/iPod into an external speaker.
What other uses does this thing have?

 

[GaryWA]

  What is the use for these?
http://www.ebay.com/itm/3FT-3-5mm-1-8-Male-to-Male-Stereo-Audio-Jack-Cable-for-iPod-MP3-MP4-DVD-Green-/290765541701?pt=US_Audio_Cables_Adapters&hash=item43b2fa1145
 
I am going to buy this so I can hook my phone/iPod into an external speaker.
What other uses does this thing have?

Mostly for what you're using it for. Portable device --> AUX input. They are also used for connecting a computer sound card to speakers.