ipl2 is the product of the merger between the Internet Public Library and Librarians' Index to the Internet. Not only does ipl2 present a rich directory of web sources on a vast number of subjects, they also offer a question answering service manned by platoons of librarians and knowledgeable volunteers.
ODP is the largest human-edited directory of the Web on the Internet. The content is edited, updated, selected, and otherwise maintained by a large community of volunteers dedicated to the mission of providing access to the best information available on the Web.
About.com is an example of a service that pays it's contributors. This is a service with a vast amount of information created by thousands of people with interests in the subjects presented. A very useful site whose pages populate the search results of many other popular search engines.