Tax Lien Associates, Inc.
Offers a variety of services and investment products to U.S. municipalities and investors, including acquisition and brokerage, marketing tax-lien land, portfolio management services and software, and an investment fund.

LienSource
Offers subscription lists of property lien sales, in some localities.

Arizona Property Tax Lien Primer
Information from attorney Mark Manoil about the legal and practical aspects of property tax liens and certificates of purchase as real estate investment. Includes news articles and links to related resources.

POA Properties LLC - Able Tax Sales
Offers information by paid subscription about tax lien certificate and tax deed sales, and how to get started investing in them.

BargainProperties.ca
Subscription-only database of real estate in Canada that is now available due to tax arrears.

LandLordTax.com
Offering assistance to property investors and landlords with the completion of their tax returns.

Tax Lien Certificates Network
Website provides resources and information exchange for investors interested in buying and selling tax-defaulted paper. Includes related links; registration required to participate in the network.

JohnBeck.net
California attorney offers educational materials and seminars on tax-sale investing.

The Creative Investor Tax Lien Group
FAQ, forum, and e-mail list for discussions about investing in tax liens.