You can only have one account
So you can only be a referal for one person, unless you go around using differennt email adresses and stuff like was posted before. My relatives/I have done Ink, Blockbuster, AOL, and Netscape.
Blockbuster is 2 weeks of free movies, you can cancel online (it was 3 day shipping for me so I didn't get much).
AOL can be cancelled by fax, which is much easier than having to deal with people over the phone
http://www.aol.com/support/index.adp?toc=billing&page=23 (I don't think AOL is up anymore)
Netscape sends you to some Indian person that reads 5 pages to you about why you should stay with Netscape
and Ink, came in like a week I needed ink anyways, so it's a good deal.
The site that is running this, Gearlive also has Conga Lines for other free sites (freeipods.com, ect) the way they work is that you sign up with the referal pasted in the topic and get put at the end of the list. When the top guy is done it goes down to the next guy on the list, however these die pretty quickly because of the limited # of people, especially when you need a lot of referals per a person.
Also if you don't like any of the gifts offered right now they will be adding more, also you will be able to get more than one gift, but every time you order a gift all your referals are deleted. So if you got 12 referals you can't order a Mac Mini and save 1 referal you have to start over again.