
An amazing wealth of collector's resources for American Girl, put together by Sail-Away. This is the site for all things AG, yes!- even Bitty Baby, the AG Minis, Girls of Many Lands, and more! This site also has the AG Playthings! message board, with tons of reviews, advice on doll restoration and care, and a sell/wanted forum. The AG Playthings! message board is very well-designed and organized, with many easy-to-navigate sub-forums, making finding answers to your questions a cinch. Reviews are categorized by doll, so it is easy to find out what others thought about that item you are considering.
This site has the link to Meg's fabulous AG Historical Collector's Guide, which you can also download if you want a desktop copy. Meg's Guide is an excellent companion to Curt's Guide (below), as they are "good" for different functions. Meg's Guide has full catalog text and pictures for every historical and AGT item ever made, along with a very good summary of the history of the company and how the packaging has changed over the years.
THE website for 18" vinyl doll collectors. This website has, hands-down, the best collection of reviews and photos all in one place for 18" vinyl play dolls, both AG and slim-bodied size. Compare and contrast AGs with Life of Faith, Heidi Ott, Maplelea and more! See why spending almost $100 for an AG or other high-quality vinyl play doll is worth it by comparing AGs to Springfield and My Generation dolls. Check out the lovely slim-bodied dolls such as Carpatina, Magic Attic, Just Pretend, and more! Each doll is profiled in detail, giving very clear, understandable charts concerning information like manufacturer, dates of manufacture, original price, wig quality, body articulation, and so forth. Each doll also has a considerable essay-format review and plenty of photographs. If you are a fan of Stardust Classics, this is a must-see website, because she has scans of the catalogs and full checklists.
As if the huge list of doll reviews and photos weren't enough, there is a "Doll Restoration Wizard" that will walk you step by step through the process of turning that stinky, dirty, frizzy-haired ebay rescue into a sleek, well-groomed dolly! Clear instructions and photos on everything from basic doll care (cleaning of vinyl, body, and hair) to the more drastic surgeries of rewigging and restringing are given.
A fantastic source for the AG Historicals, Today, and Hallmark lines, including rare items such as the baseball promotional giveaways. Created for his daughter, the website has all the latest news concerning American Girl and a full catalog of all the historical and AGT items ever made. It is formatted in a very intuitive and pleasing design, with a brief description of each doll and pictures of all the items for each doll. Some of its unique features: "Special Items" page for Hallmark, AGP and AG Club Items, and baseball giveaways; "Dresses" page for all the retired Dress Like Your Doll line for girls; "Trading Cards" page that has all the cards (this is the only site I know that has this). Check out the "Gallery" page for a real treat- you get to see over 100 images of Pleasant Company history through catalog covers and pictures, going back to 1988. The "Never Were" page is a lot of fun- see what fun items Curt and his daughter dreamt up that should have been made by AG, but never were.
This is a great companion to Meg's Guide, because Meg's Guide will tell you all the details about the items (like what bits and pieces go with a retired outfit, as well as the original price), whereas Curt's Guide is great for quick reference, the very unique pages described above, and its wish list capacity.
Unlike other websites, Curt's Guide does not have a checklist, but rather the capacity for you to design personalized wish lists, complete with pictures of each item. You can create an entire catalog of everything ever made for yourself, if you have enough time, paper, and ink. This could be quite handy for birthday and Christmas lists for kids, too.
A great selection of helpful websites, including non-AG clothing, doll games and activities, and dolly first aid. This is the best list of websites I've come across so far.

American Girl Historical Doll Clothes
Dollies Dressmaker- my personal favorite- affordable, understated elegance and always excellently made. www.dolliesdressmaker.com and on ebay under dolliesdressmaker
Ebay sellers: keepersdollyduds, racharney, sdls275, sewaddicted2
Other online stores: A Confederate Belle http://aconfederatebelle.webs.com/index.htm; Terra Experience www.terraexperience.com
Antique Furniture
My Little Dream- Antiques for dolls of all sizes. Her items are wonderful- she has furniture, dishes, sewing items, everything you can imagine. She also has a generous layway program. It really *is* a dream! www.mylittledream.com
Bleuette
Ebay sellers: chasandsally, jkengblom, houseofmissymouse
Crafting for Dolls
See "Crafting Resources" page.
Fantasy Outfits and Doll Repaints
Buttons and Butterflies- Fantasy clothing for a variety of dolls, including slim-line & AG sized 18" vinyl play dolls, Ellowyne, BJDs, and Kish. Can't recommend Karen's items enough- they are fantastic, well constructed, imaginative, and carefully detailed. www.freewebs.com/creativeoriginalsbykaren and on ebay under buttons_and_butterflies
Carpatina- Fantasy 18" slim-line play dolls and basic fantasy clothing for slim-line and AG dolls. www.carpatina.com
Wendy's Daydreams- Wonderful repaints, particularly of Ellowyne and Kish dolls. www.wendysdaydreams.com and on ebay under wendys_daydreams
Handmade Miniatures- Antique Reproductions
The Historical Doll- This is the stuff I offer. See the crafting resources page for an album of items that I make and put in my ebay store. I also offer kits four times a year; you need to email me to get on a mailing list if you want kits, as these are only offered to the mailing list and friends on the AGPT forum. I try to make my items affordable yet still accurate and detailed. http://myworld.ebay.com/thehistoricaldoll
Heirlooms by Susan- Susan makes elaborate Victorian reproductions, often very French. They are often sized in 1:12 scale, but sometimes available in larger sizes such as for Bleuette or larger antique dolls. I have never bought anything, but she consistently commands very good prices and the items look amazing. Definitely worth watching even just for fun and ideas- I find her to be a real inspiration. Her 1:12 scale miniatures are some of the most detailed I have ever seen. http://stores.ebay.com/HEIRLOOMS-BY-SUSAN_W0QQssPageNameZstrkQ3amefsxQ3asstQQtZkm
Kitchens for Dolls
Ebay sellers: farmhouse_mouse, hissyphitt, outtagramsattic, toomossy1

A few tips on searches on ebay that will consistently turn up good items for historical AGs:
Tips about finding accessories and furniture:
Create a free website at Webs.com