Etsy
If you like one-of-a-kind items, Etsyis a good Web site to visit.   Individuals have their own “shop” on the site and they sell handmade goods, vintage clothing, purses, jewelry, and too many other things to list.  This site is browsable in a few different ways: by category (clothing, bags, candles, etc.), through the search bar, and by seller.  In addition, you can post an idea of what you want with the price you are considering, and sellers can bid on making it for you (I haven’t used this feature yet).
 Now why would a Thriftista be interested in this store?  I’ve found some very nice one-of-a-kind purses on this site for under $50 (including shipping).  There is also a nice feature that allows you to narrow your search by dollar amount (why would I want to see things that are too expensive?).
Here are two warnings about this site—some of the handmade items are not as professional as others and some items are NOT cheap (I mean, inexpensive).  A few items are WAY out there too (my favorite is the orange furry purse), but good for a laugh.
(My favorite vendor is a friend of mine: Pretty Theory. Her pendants are a great stocking stuffer/party favor idea.)