Here's the deal:
Sign up for the following trial offers:
1. Complete Home - $20 Lowe's giftcard for $1 trial
2. Buyer's Advantage - $10 Target giftcard for $1 trial
3. Privacy Guard - $30 Staples giftcard for FREE trial
4. Clever Clubhouse - $20 Blockbuster giftcard for $1 trial
5. Great Fun -$20 Exxon Mobil giftcard (I know it says $10 on the offer but $20 came!) for $1 trial
You can use a prepaid Visa or Mastercard or a virtual credit card number if you are worried about using your real credit card number. Check with your card company as many now offer virtual credit card numbers. I signed up on a Saturday for all 5. I received confirmation emails right away. On Monday I received welcome emails from all 5 companies. On Tuesday, I received an email titled "Here's how to get the item you requested". You submit the information (including your membership number so make sure you have that written down) via online form, and for me, my giftcards arrived 11 days later.

Just a heads up - I've been told that these offers come up occasionally when doing a larger online offer (see my Wii/Wii Fit post here) so if you're thinking about doing more of those type of offers you may want to hold off on doing these.