Tapestry Resources for Tools, Warp, Weft Yarns: 

Anahera Yarns, crewel-weight needlepoint worsted wool, made in New Zealand.  Heavier (thicker) than Appleton, available through wholesale distributor, Fleur de Paris, based in Los Angeles, CA  

Appleton Yarns, crewel-weight 2-ply needlepoint/embroidery worsted wool in over 400 colors.  Made in the United Kingdom, available in the United States. Several retail places on-line, such as The Wooly Thread.  Wholesale distributor:   Fleur de Paris

Australian Tapestry Workshop (formerly known as Victorian Tapestry Workshop) yarns are thinner, huge color range for weft bundles.  You can now directly order from them, but bear in mind that this entails overseas shipping and customs.

Between and Etc. (formerly known as Fine Fiber Press) owned by Kathe Todd-Hooker  has tapestry tools, looms, warp and weft yarns:

Tapestry Tools:  Different sizes of Gobelins- style bobbins, including some brass-tipped ones, as well as the Aubusson style "bone" bobbin, awls, various hand beaters, and other tapestry-related tools.

Yarn cotton seine twine warp as well as weft Alv Norwegian wool that is a 2-ply worsted about 14/2 in size.  

Brown Sheep, based in Nebraska, makes the 3-ply Waverly Needlepoint worsted wools (you will have to un-ply these to do color blending) as well as Top of the Lamb rug-weight wools.

Davidson Old Mill Yarn –3 and 4 ply wool warp

DMC Embroidery Floss is a cotton alternative for weft, with 6 strands you can separate out to make new color blends.  Available through craft or fabric stores such as Joanne’s, Michaels, etc.

Glimakra USA carries both Farö and Mora weft wools.  Faro is a singles, and Mora is a lace-weight worsted.   Also cotton seine twine warp.

Magpie Woodworks for weaving forks, made in three different widths.

Norsk Fjord Fiber has cotton seine twine warp in 12/12 and 12/6, linen warp, as well as Vevgarn, a 2-ply wool for weft from Norway.  

Tandy Leather Company carries awls

Vavstuga Weaving School of Shelburne Falls, MA carries Borgs wool yarns, Swedish cotton seine twine warp.

The Woolery of Frankfurt, KY carries Gobelins-style bobbins.

Weavers Bazaar  in the United Kingdom carries fine worsted wools in three different weights:  Fine 18/2,       Medium 8/2 and7/2, Heavy 5/2 and 6/2

Weaving Southwest carries weft yarns that are hand-dyed churo wool in rug weight and a singles weight.  They also carry wool warp.

Yarn Barn of Kansas  carries Le Clerc Gobelins–style tapestry bobbins,  wool warp.

Ymm Yarns  from Australia, thin, 2 ply wool for weft bundles.  Janette Meetze, who lives in Oklahoma, carries these yarns.