Software to make microphone input sound be outputted through speakers?

[Sheepiedog]

I'm looking for some software that takes the sound received by a microphone and plays is back through headphones/speakers. I will use this to eliminate the "clogged ear" effect of wearing headphones so I don't have to yell when talking on applications such as skype.

I have a new 15 inch Macbook Pro

 

[Jodles]

Although a little elaborate, you could try to use something like Reaper (reaper.fm). But I don't know whether Skype has taken all control over microphone or not...

 

[Jolly Jimmy]

LineIn can do this. Only use it with headphones though, using a mic and speakers will generate feedback.