(There are also some more links on this page)

This is not an exhaustive list but includes some which I have found particularly interesting, with links to other sites 

http://astrosurf.com/buil (Christian Buil)

http://home.freeuk.com/m.gavin/ (MauriceGavin)

Visual Spec (Valerie Desnoux)

www.astrosurf.com/aras/ (Astronomical Ring for Access to Spectroscopy)

http://spektroskopie.fg-vds.de/index_e.htm  (VdS Spectroscopy section)

http://www.astrospectroscopy.de/   (ASPA - Ernst Pollman)

http://spectroscopy.wordpress.com/  (Club of Amateurs in Optical Spectroscopy - ESO)

http://www.astrospectroscopy.eu  (Lothar Schanne)

http://www.astronomie-amateur.fr/  (Francois Teyssier)

http://www.ursusmajor.ch/astrospektroskopie/richard-walkers-page/  (Richard Walker. Some excellent documents in English at bottom of page)

http://www.stsci.de/convento/    (The Convento  Pro-Am spectroscopy campaign group)

http://saser.wholemeal.co.nz/  (The Southern Astronomical Spectroscopy Email Ring supporting Pro-Am campaigns for southern hemisphere observers)


Forums where amateur astro-spectroscopy is discussed (in no particular order) 

(If you know of any others, please let me know)

http://tech.groups.yahoo.com/group/amateur_spectroscopy  (English language group, mainly but not exclusively astronomical, largely superceded by other forums now)

http://tech.groups.yahoo.com/group/spectro-l/  (French/English language group to support the Astronomical Ring for Access to Spectroscopy (ARAS) )

http://www.spectro-aras.com/forum/  (French/English forum for the ARAS group. A key forum for those interested in Pro-Am projects. Also support for Shelyak spectrographs and ISIS, Visual Spec Audela/SpcAudace software) 

http://tech.groups.yahoo.com/group/SBIG-SGS/  (English language group for the SBig SGS spectrograph)

http://tech.groups.yahoo.com/group/spectrohelioscopes/ (English language group discussing design construction and use of spectrohelioscopes)

http://tech.groups.yahoo.com/group/staranalyser/ (Mainly English language group for the Star Analyser spectrograph)

http://tech.groups.yahoo.com/group/astronomical_spectroscopy/  (Group primarily for the L200  kit spectrograph but also general topics)

http://spektroskopie.fg-vds.de/forum/  (Mainly German with some English language forum supporting the VdS spectroscopy section. Some high level and professional technical knowledge here)

http://forum.astronomie.de/phpapps/ubbthreads/ubbthreads.php/forums/73/1/Spektroskopie_Meeting_Point  (Spectroscopy section of the German astronomie.de amateur astronomy forum)

http://www.astronomie.ch/forum/spektroskopie.php  ( German language  Spectroscopy section of the forum of the Swiss amateur astronomical society (SAG) )

http://ukastroimaging.co.uk/forums/index.php?board=84.0  (Spectroscopy, Astrometry and Photometry section of the English language ukastroimaging forum)

http://stargazerslounge.com/forum/75-radio-astronomy-and-spectroscopy/  ( The Spectroscopy and Radio A stronomy section of the english language Stargazers Lounge   astronomy forum)

http://www.cloudynights.com/ubbthreads/postlist.php/Cat/0/Board/variables   (Officially the Variable Star and Radio Astronomy section of  the English language cloudy nights forum but spectroscopy is also discussed here.)

http://www.iceinspace.com.au/forum/forumdisplay.php?f=40  ( The Spectroscopy and Radio A stronomy section of the Australian  "Ice in Space" astronomy forum)

http://www.webastro.net/forum/forumdisplay.php?f=69  ( A French language forum)

http://tech.groups.yahoo.com/group/RSpec_Real_Time_Spectroscopy   (Support group for the RSpec real time spectrum display and analysis software)

http://tech.groups.yahoo.com/group/spectro-eShel   (Support group for the Shelyak instruments eShel fibre fed echelle spectrograph)

http://www.audela.org/phpBB2/viewforum.php?f=9   (Forum for the SpcAudace spectroscopic data reduction program  -  French)

http://www.astroforo.net/viewforum.php?f=89  (A Spanish language forum)

http://quasar.teoth.it/forums/viewforum.php?f=22  (An Italian language forum)
https://groups.yahoo.com/neo/groups/Spectroring/info  (Primarily an Italian language forum)
http://www.iceinspace.com.au/forum/forumdisplay.php?f=40 (The spectroscopy and radio astronomy section of the Australian forum "Ice in Space"
http://www.aavso.org/forums/variable-star-observing/spectroscopy  (The spectroscopy section of the AAVSO forum)
https://uk.groups.yahoo.com/neo/groups/astrobodger/info  (Yahoo group in support of the BASS spectroscopy data reduction software)
https://groups.yahoo.com/neo/groups/SocAstroSci/info  (Yahoo group of the Society of Astronomical Sciences, set up initially to promote interest in spectroscopy primarily in the US)
http://lists.wholemeal.co.nz/cgi-bin/mailman/listinfo/saser  (email list in support of the SASER southern hemisphere Pro-Am group)
http://spektroskopieforum.vdsastro.de/viewforum.php?f=32   (Forum in support of the Convento Pro-Am group)