Here are a few not-for-profit LDS singles resources we have encountered in our research. *LDS Living Single is not responsible for content in the sites below.

About.com
About.com is a resource for LDS members, updated and monitored by LDS members.
Black Single Mormons
An independent website with resources for black Latter-day Saints.
Blacklds.org
A web site dedicated to black members of the Church of Jesus Christ of Latter-day Saints.
Boise LDS Singles
Resource for LDS singles in the Boise, Idaho area.
BYU Single Alumni
Information for BYU single alumni. Non-BYU alumni are welcome to participate.
Washington DC LDS Singles
Resource for LDS singles living in the Washington DC area.
Arizona Singles
Resource for LDS singles living in the Phoenix, Arizona area.
Genesis Group
A site provided by the Church of Jesus Christ of Latter-day Saints, for black members.
German Singles
Site for LDS singles in Germany (it appears to be outdated).
Jen Magazine
Online magazine for LDS women, including resources for singles.
LDS Linkup
A free way to reconnect with LDS friends, married & single, or meet new people.
LDS Singles Calendar
Shows LDS singles events by region in the USA.
Lehi Single Adults
Website for singles in the Lehi, Utah area.
Queensland, Australia
Website for singles in Queensland, Australia. It's a bit outdated, but does have some information.
Central Virginia
Website for singles in the Richmond, Virginia area.
Deseret Singles
Website for singles in the San Francisco, California area.
Singles on the Go
Some information on singles activities in the Salt Lake City, Utah area.
The Social & Cultural Construction of Singlehood among Young, Single Mormons
A research paper on being LDS and single.
Mt. Timp FHE
Singles activities for 40+ singles in Utah Valley.
Multi-Stake Singles
Singles activities for 30+ singles in Utah Valley.