UPDATE: I've created an Etsy Vintage Directory, with housewares & more clothing options. Many sellers below are not in the directory, but I still recommend checking them out.
A few weeks ago, Bethany of Road Trip Journal suggested I check out the vintage fashion on Etsy. I've meant to do that for some time; when I started covering vintage, Etsy was about to shut down their vintage category. Things have changed a lot since then, however, and with eBay hiking its rates up yet again, Etsy has become a popular haven for frustrated vintage sellers.
In this case, what's good for sellers is also good for buyers. Etsy stores have reasonable prices (i.e. no insanity-inducing auctions), and buyers have the advantage of seller ratings & the site's easy-to-navigate format. Below, some recommended vintage clothing sellers (the official Etsy Vintage Directory is now here):

Burgundy maxi dress, $52.00; green high-waist tweed skirt, $22.00; lace ruffle cami, sold; green silk shirt, sold.
1. Ma Petite Amy: A well-edited and extremely well-presented collection (that styling!). Owner Amy said on her blog that she's considering moving from Etsy to eBay, so we'll see what happens (via A Cup of Jo).
Yellow grey stripe dress, $36.00; green silk dress, $65.00; 1960s platforms, $24.00; floral tea dress, $26.00; tiered dress, $34.00.
2. Pretty Little World: A large collection of bright, pretty pieces, and the prices are good. She also has a nice fashion blog.
Diane von Furstenberg heels, $30.00; striped dress, $30.00; bow flats, $20.00.
3. Dewberry Vintage Fashion: Another cute store, with particularly good shoes.

Orange spring coat, $25.00; 1980s denim Guess skirt, $18.00; 1970s red suede skirt, $16.00.
4. OurLadyoftheUnderpas: Aimed at younger buyers, this store features bold pieces for super-low prices, modeled by a diverse set of body types. They also have covetable items in larger sizes (like the coat and red skirt above).

Navy & gold splatter dress & jacket (not shown), $75.00; yellow 1950s silk dress, $24.00; chevron-striped day dress, $35.00.
5. Road Trip Journal: The catalyst for this post happens to have an awesome Etsy store. I particularly liked her write-ups--she details each item's flaws and even goes into the history of certain pieces.

Altered 1970s Gunne Sax ballerina dress, $100.00; red & white wedge leather shoes, $30.00; 1960s yellow bead shift (sold).
6. Enigma Vintage (CLOSED): Excellent descriptions, good pieces, and dreamy photography. The seller really won me over, though, when I visited her blog & saw that she loves the Tightwad Gazette too.
Black leather ankle boots (sold); flower print high waist skirt, $39.00; grey ruffle cotton blouse (sold).
7. Ramona West Vintage Boutique: Clean styling and a boho-chic vibe.
Pink embroidered blouse, $36.00 (reserved); Moroccan jeweled flats, $42.00; the Senora dress (sold).
8. Oh, Leoluca! (via A Cup of Jo): Brightly colored European vintage from artist Teresa Hu (who's originally from Atlanta). The amazing photographs are by Mariel Lohninger.
For more Etsy Finds, check out our archives. For more vintage, see the Online Vintage Clothing Directory.