1. Salvation Army/Goodwill : I feel like a lot of people really overlook these stores for a great place to find vintage clothes. You might not find a Chanel bag or a Dior scarf, but you can def. locate unique and eclectic pieces. The best part is they are usually under $5 and go toward a good cause.
2. Antique stores: Once again a lot of people think antique stores are strictly furniture and other goods, but they can be a great place for vintage accessories such as jewelry, bags, and furs. The next time you see one I suggest you walk in and browse around.
One of my favorite's is the 5&10 antique market (http://www.5n10antiques.com/) in Northeast, MD.
3. Vintage stores: Probably the most expensive of the group, vintage clothing stores are amazing. My favorites include Malena's Vintage Boutique (http://www.malenasboutique.com/) in West Chester, PA, Rags to Riches UPSCALE Resale (http://www.ragstorichesresale.com/) in Wilmington, DE, The Green Eyed Lady (http://www.shopgreeneyedlady.com/servlet/StoreFront) in West Chester, PA, and Cottage Home (http://cottagehome.typepad.com/) in West Chester, PA.
4. Tag/Estate Sales: A great place to find second-hand clothing and often times great estate jewelry.
All of these places are great for finding vinatge clothes and remember the hunt is half the fun. Never feel ashamed or embarrassed for buying second hand clothing. You are making someone's trash your treasure and this speaks volumes for your creativity.