Links between two sites, often based on an agreement by the site owners to exchange links.
Reciprocal links are based on an agreement by two sites to link to each other. Reciprocal linking is often used by small/midsize sites as an inexpensive way to increase Web site traffic and link popularity.
see also: SEO Tools
Webmaster World : Link Development – discussion of topics related to acquiring links (not a place to exchange links)
What Makes a Site Link-Worthy?
ClickZ (December 12, 2000)
Links: Cheaper and Better Than Banners
ClickZ (November 29, 2000)
What Your Link Request Should Contain and Why
ClickZ (November 9, 2000)