Ancestry/Genealogy

I did this when I first got started:
1) Call them, don't sign up online.
2) Prearrange the termination date. This way, you don't have to call to stop the membership and prevent them from charging.
3) If you decide you want to continue, call again AFTER the termination date. They will be anxious to get you hooked back up and offer really good deals.

In my case, when I first signed up, I had a coupon for a massive discount for three months. I didn't want to have to remember what the end date was and had heard the horror stories about not being able to contact Ancestry to cancel. The customer representative who talked to me offered the prearranged termination date. It worked - on that date I tried to sign in (as I thought, I forgot the date my membership ran out) and couldn't.

I called in, and they gave me 50% off a regular annual membership so I got sucked back in but again I set the prearranged termination date. The next year I called and they gave me a great deal off the World membership - which I needed because I was begining to research past when my ancestors got to American and I had Canadian relatives I needed to find. As long as they think you might just bail on them - which is easy to do with the preset termination dates - they will offer discounts to keep you.

Meanwhile, I am tempted to try out Macavo.com. It's supposed to be free for access to all the records, but you get limited search capabilities unless you pay for a membership. So far, I've only signed up for the free version but haven't looked at much yet.