You've probably been spammed by offers of a free ipod. They claim all you have to do is sign up for their site, then sign up for one of their offers, and then refer friends who do the same. I've linked to one of these sites below, and they do give out free ipods to people that complete the requirements. Here's the strategy that you should use:
1) Sign up for the service using an email address that you don't use often. This account will very likely become the target of spam. They have to pay for all those free ipods they give away somehow.
2) Get a group of 24 or more friends together. This is very easy if you are in college, but it may require some time to form a crew with instant messenger.
3) Select 4 accounts to become the "winning accounts." Split your group of 24 into 4 groups. Each member of a group signs up using the same referral website address. The member with the winning account just gives out his referral code to his group members.
4) Everyone completes an offer. Select the offer that is least expensive (sometimes free) and can be canceled quickly. Sometimes there are some pretty decent deals, just as long as you cancel as soon as you are allowed to. Many of these offers are something like "try this magazine for 1 month for $1," so nobody in your group can claim they can't afford it.
5) You should now be eligible for 4 free ipods. Splitting them up is up to you. You can do a lottery, or do some sort of tournament (I've done a Texas Hold Em tournament and a Madden 2006 Tournament). Alternatively, you can sell all the ipods on ebay (where they sell for close to retail, and split the proceeds among all members.
6) Find another site, do the same thing with an even bigger group of friends.
ipods.freepay.com - Get a FREE iPod!