Try some podcasts on topics the students might like. Look for podcasts with interviews or shows with two or more hosts.
You can plug the podcast into a free ware audio edittors like Audacity and chop it up.
Or like Emile said just buy a mic. and have at it. That's what I did for audio over at
www.hospitalenglish.com
If you have Skype you can use that and record conversations with friends. There are programs you have to pay for and some free ones that will record Skype calls.