If thrifting interests you there are many great sources these days to find antiques online. 1stdibs is an online antique shop with inventory that is always changing. And ebay has many great buys. If you are looking for a specific piece Google searches can sometimes be fruitful, but all of these options will most likely need to be shipped to your home which results in packing material and fuel. I recommend looking local first, you will be supporting your local infrastructure, as well as negating the need for shipping altogether. Local options beyond thrift stores, and antique shops include, Craigslist, or the classifieds section of your local newspaper. I have found some great deals on local furniture that I have re-purposed.
#1 I found this chair for $8 dollars at a local thrift store, I painted it white and purchased the green bamboo print at the same shop a few weeks earlier for $.50. It adds charm to a chair that was rather bland before. What a deal!
#2 This chair came from a very small thrift store a few blocks from my home, it was brown and had chipping paint. I painted it to match chair #1 so I could use them in my dining room.
#3 This option came from the same shop as chair #1 and was neon orange when I spotted it. It has been painted blue and green and I have used it as an outdoor chair. I got it for a steal which makes it even sweeter!