Many folks in the pf blogging community have written about prosper.com, an online peer-to-peer lending community. But if you're thinking about lending money to a relative or friend, a better option would be Massachusetts based CircleLending.com. You can read more about the company's services in a recent article in the Chicago Sun-Times.
According to the CircleLending website, you can use the company's services to structure mortgages, personal loans or small business loans. For a minimal fee, CircleLending will set up a payment plan, handle the loan documentation and process the payments for you. They'll even send out e-mail reminders and late payment notices for you.
Sometimes it's just better to put things in writing, even if it makes for an awkward conversation on the front end. My parents are still lamenting the fact that my brother hasn't even offered to pay back a $5,000 loan. I guess he thought it was a gift.