Amazon was tight-lipped about the deal. An Amazon representative would not disclose the size of its investment or elaborate on Amazon's interest in the site.
The online retailer has been wading into new territory recently. In a bid to give Google, Yahoo and Microsoft more competition in the Internet search and directory arena, Amazonlast year. Last month it introduced featuring photos of storefronts in 10 U.S. cities.
Web logs, or blogs, have become, and Amazon's investment in 43 Things signals the Web retailer is taking an interest in the trend. Some e-commerce executives predict with links to favorite products and recommended shops.
But the founder of 43 Things, a former Amazon executive, said the sites are completely separate.
"We don't spend our time thinking about Amazon; we spend our time thinking about what we're building at 43 Things," said Josh Peterson, the chief executive of Robot Co-op, the parent company of 43 Things.
Peterson left his post as director of personalization at Amazon about four years ago and launched 43 Things on Jan. 1. His inspiration for the site came after finding that people often run out of interesting things say on blogs, he said.
With 43 Things, people simply publish a list of things they want to do--up to 43 items long. They can add comments, check off items they've completed and browse other members' lists. More than 7,300 people have created lists, which anyone can view. Items range from the general ("get organized") to the specific ("read more Kierkegaard"). The most ironic: "Spend less time fooling around on the Net and more time actually working." Some 175 of members of the site share that goal.
The site also incorporates online community features. For instance, add a goal to your list and a tally of how many other members share that goal appears right next to it. Every item is also hyperlinked to the profiles of other registered members who share the goal.
In addition to to-do lists, members can post pictures, their locations, e-mail addresses and links to other Web sites, creating mini-profiles. They can post comments on other members' pages too. The company is exploring more ways to let its members contact one another, Peterson said.
The company offers all of this free of charge to it members, making money from online advertising.