Elements Art Supply
1025 Baxter St.
Athens, GA  30606
(706) 546-1310
For those living in the larger metro Atlanta area this place carries the widest and best selection of alabasters and other soft carving stones, as well as some varieties of marble.  And naturally, hand and pneumatic carving tools for the sculptor.
FINDSTONE is a nexus of contemporary sources in the commercial stone industry.
One of the most useful aspects of this site is a searchable database of images of many different types of commercially-quarried stones throughout the world. 
http://www.tiranti.co.uk/
This site is for a sculpture supplier in the United Kingdom which forges their own line of chisels, including mallet-head chisels that are so ideal for carving soft stone.
http://www.sculpt.com/
  The Compleat Sculptor
 
At this New York supplier you will find a wide  selection of sculptor's tools, supplies, and  carving  stone, including imported mallet-headed chisels.
These folks carry tools and supplies for the stone industry.
If you want to go into the stone floor polishing/countertop
making end of things they've got it all -- though they do
have some stuff a sculptor might just use as well.
Several warehouses located in North America, including Atlanta.
Don Dougan   -   sculptor
www.dondougan.com
TROW AND HOLDEN
are the folks that invented the pneumatic carving hammer over 100 years ago and continue to provide
top-of-the-line tools for the stone carver.
Joseph and Sons
When next in Paris you should
stop by this tool supplier across from
Pere Lachaise cemetery and look at
their selection of stone working tools -
especially the traditional hand-forged
mallethead and wood handled chisels
for carving soft limestones.
Located in New York,  SCULPTURE HOUSE
has imported and sold sculpture supplies by catalog for many decades - their 'house brand' tools are in turn available from many other suppliers across the country. 
"Books you thought you'd never find . . . "

A book is an essential tool, and when it is out-of-print Alibis' network of booksellers helps you find it and then handles the sale.
Located in West Palm Beach, Florida, Montoya offers sculpture tools, supplies and services, including carving stone.
To say their specialty is woodworking is an understatement, but this unusual neighborhood hardware store in Atlanta carries a wide variety of tools that any sculptor might find useful.  They have built a nationwide reputation as a mail-order woodworking supplier, and they provide numerous hands-on masterclasses in woodworking-related subjects.

This stone carving supplier in Rome is one of the few places you can still find a traditional Bow Drill, in addition to a complete line of Italian-made handtools and pneumatic hammers.  They also carry powertools and supplies for working mosaics. 
The website is in both Italian and English.
The list of suppliers below is far from complete, but these are all companies with whom I personally have done business with over the years.  I have found that all of these firms are reputable and each one offers something unique.  However, as death and taxes are the only things that don't change, caveat emptor.

  Note: the listings are in no particular order other than what         
simply looks good on the webpage when I add a new listing.
LINKS TO OTHER SITES YOU MIGHT FIND OF INTEREST:
RESOURCES & SUPPLIERS
an excellent site for stone sculpture and stone links
Zepti - web search engine

a catagorized search engine.
Highland Woodworking Link
Free spam-free newsletter that will help you deal with Windows inevitable problems. 
Though they specialize in kits and videos for lifecasting, these folks also carry all types of other moldmaking and casting supplies for the sculptor.
For the best in Lifecasting Kits, supplies, books, videos and resources ... please visit artmolds.com