Organizations:

americanmosaics.com
mosaicmatters.co.uk
mosaicartists.org
craftdirectory.org

Artists:
glassmosaictileart.com
daybreakmosaics.com
bluelotusarts.ca
mikaarts.com
mosaicworks.com
mosaicwares.com
flowersoup.com
mozaicdesigns.com
icmosaics.com
madplattermosaics.com
mosaicando.com
truemosaics.com
riversonfineart.com
cbmosaics.com
faducci.com
stevosphere.com

Materials & Instructions:

marylandmosaics.com (My Favorite)
glassmosaictiles.com
macglue.net 
mosaicartsupply.com 
mosaic-tile-guide.com
artfulcrafter.com
mountaintopmosaics.com
mosaic-tile.com
happycraftnsmosaicsupplies.com
tilemosaics.com
witsendmosaic.com
mosaicsupply.com
tabvlarasa.com
smalti.com
mosaicstation.com
mosaictools.com
monstermosaics.com
mosaicsource.com

General Interest:

findartinfo.com
fotosearch.com
elvesofester.com
nikidesaintphalle.com
ucmmuseum.com
MosaicAtlas.com