Tasic Sinisa's excellent page on SDR radios and other goddies.
http://yu1lm.qrpradio.com/

Tiny SDR Hardware
http://www.qrz.lt/ly1gp/SDR/

SDRIQ Radio
http://www.rfspace.com/sdriq.html

SDRZero
http://py2wm.qsl.br/SDR/SDRZero-2.html

High Performance SoftWare Define Radio, home of Ozy and Janus and other high performance SDR components.
www.hpsdr.org

HPSDR.ORG Wiki
http://hpsdr.org/wiki/index.php?title=HPSDRwiki:Community_Portal#CASMIR_...

HamSDR a site involved with TAPR, HPSDR.ORG, and Flex Radio
www.hamsdr.org

Flex Radio home of "PowerSDR" software.
http://www.flex-radio.com/

Rocky SDR Software
www.dxatlas.com/rocky/

SDRadio software
http://digilander.libero.it/i2phd/sdradio/index.html

Winrad SDR Software
http://www.weaksignals.com/

KGKSDR Software
http://www.m0kgk.co.uk/sdr/index.php

Elink Software
http://www.g3ukb.co.uk/

GNU SDR Radio software
http://www.gnu.org/software/gnuradio/gnuradio.html

Home to SDR Shell software for Linux
http://ewp.homelinux.net/sdr-shell/

uWSDR Linux SDR software
http://uwsdr.berlios.de/