A list of vendors for fabrication supplies

This list was taken from the old wiki. It might be outdated and is mainly targeted at buyers in the USA.

Photolithography masks

Laserlab, Inc. (http://laserlab.com/products_and_services.php) Photoplots with up to 8000 DPI

Harmony Cleanroom (http://www.harmonycr.com/) Lint-free swabs, wipes, gloves, etc

Local grocery or home improvement store Whink brand rust remover contains 2-3% HF.
Duda Diesel (http://www.dudadiesel.com/) HCl for metal etching.

Injectorall (http://www.injectorall.com/) Shipley SP24 positive photoresist. DNQ-novolac based, peak sensitivity at 405nm.

Duda Diesel (http://www.dudadiesel.com/) Technical grade acetone and isopropanol. May have lower impurity levels than hardware/paint store grades.
Local hardware store Acetone, denatured alcohol. May have lower purity.
Harmony Cleanroom (http://www.harmonycr.com/) 99% isopropanol / 1% DI water.
Pharmacy or some grocery stores Isopropanol (rubbing alcohol). Go for the highest concentration you can get (91% is ideal)

MTI (http://www.mtixtl.com/) Materials science related supplies including wafers up to 6 inch diameter sold in units of one.
University Wafer (http://www.universitywafer.com/) Has a wider selection than MTI but minimum orders are high.
Singapore Optics Shop (http://optics.sg/main.html) This supplier does not have much of a minimum order (Keep orders above or equal to 5 wafers) but prices can be quite high for small wafers. They do have other wafers like Germanium and also has quite a lot of other cool stuff. They do ship to countries outside Singapore. Price will include SGD $30 handling fee.
Latech Scientific Supply (http://www.latech.com.sg/) I am putting them back on here after they have updated their information. They do have a minimum order of 25 pieces for wafers of size 3 inches and above. According to their sales representative, wafers smaller than 3 inches can be bought in small quantities. If you want to get a large amount of wafers, I suggest using Latech as their prices are cheaper than the ones at Singapore Optics Shop. They also have some lab stuff that experimenters might be interested in.
Or try one of the vendors listed at http://www.cleanroom.byu.edu/EW_Purchase.phtml or at http://mmoll.web.cern.ch/mmoll/links/silicon.htm