This article is from the of the muppets FAQ, by Craig Silverstein with numerous contributions by others.
The first URL is Henson's link to amazon.com. The second also has links to products at Amazon, but also has a section for collectibles and for trades.
However, there are many other Henson items you can buy at various places. Here are some program-related stores:
Henson-sanctioned store: http://www.henson.com/shop/index.html _Bear_ links to stores: http://www.bearinthebigbluehouse.com/shopping/shop_home.html
Specific anniversary-based memorabilia:
Anniversary watch: http://www.fossil.com/Product/Product.asp?Tier1=Collectibles&Tier2=CC&Dept%5FID=CC&Cat%5FID=c01&Prod%5FID=li2050 MuppetFest stuff: http://www.creationent.com/muppetfest.htm
And collectible stores (you may need to recombine the URLs):
Collectibles and cards: http://www.2momluvme.com/ New stuff, collectibles: http://www.muppetcentral.com/collectibles/shop/index.shtml Collectibles: http://www.scifiwarehouse.com/cgi-local/ss000001.pl?SS=muppets&TB=A&PR=-1 Plushes: http://search.store.yahoo.com/cgi-bin/nsearch?catalog=wickedcoolstuff&query=muppets Action figures!: http://www.palisadestoys.com/new/MUPPETS_SITE/MUPPET_MAIN.html More action figures: http://www.toymania.com/columns/spotlight/muppets3.shtml Busts: http://www.sideshowtoy.com/cgi-bin/category.cgi?category=muppetshome Pins, clothes: http://www.hottopic.com/store/searchSKU.asp?SSTR=muppets T-shirts: http://www.tshirtnow.com/cgi-bin/SoftCart.exe/tshirtnow/mupp.html?L+tshirtnow+hcpg5678 Assorted clothes: http://store.alloy.com/catalog/browse/productgroup.asp?PARENT=TOON_STYLE_PG&CATALOGID=TOON_TIME Disney (MuppetVision): http://www.mouseshoppe.com/ MuppetVision beans: http://www.mouseshoppe.com/directory.cfm?CategoryID=406 "Sesame Street" items: http://www.kbkids.com/w/l/snb.html?txt=sesame+street Sesame Street shirts: http://www.hottopic.com/ Various products: http://www.emerchandise.com/browse/MUPPETS/A:MUPFAQ/
Don't forget timelife.com for the Muppet videos!
And of course, the standard auction sites often have Henson stuff.
(Special thanks to Nancy Eilers-Hughes for help compiling this list.)