There are many internet trading sites which you can find using your favourite search engine. Try searching for 'internet auction site' or 'internet trading site'.
All of the sites operate in slightly different ways. Some are auction based while some are more for trading. Some are more specialised and some offer a wide range of products. Some are world-wide while others are more local.
Before you buy or offer your own items for sale it is a good idea to investigate several sites to see which will be best for you.
Craigslist is a very interesting place to check out. Go to the website, choose your location ( If you don't, you'll be looking at the default location ), and bingo. You can browse items for sale in your area, jobs, services, apartments, houses for sale, and much more.
Addition:
There are a few good places out there like eBay:
etsy.com - for homemade crafts
UniSquare.com - same setup as eBay - no listing fees
eCrater.com - similar to eBay but no auctions - no listing fees
ebid.net - available in many nations
bonanza.com - clothes and apparel mostly
There are a handful of other good ones out there, but these are some of the main ones today.
Probably from any place they sell iPods, the Internet, and places like Wal-Mart, Best Buy, and places on the Internet like EBay and other places that sell stuff.
You can buy this book at such places as Ebay or Amazon.com or any bookstore. Check your local library too.
At acquaintances' houses, but there aren't any other places that are like inns.
You can get those kinds of contacts anywhere really. Try any local costume places or places like Gloss or ebay.
You probably know these but really, you have to know about eBay and amazon and the like
It is very safe like any other place there is places you go and places you don't
They like to live in Africa, or any other places where hunting is plentiful.
I am not sure where you can buy discount pricing on designer brands, i would guess just about anywhere on line, but i am really not sure, i would try ebay, kmart, or any other places like that
You can find them in any stores that sale appliances. You can go to places like Walmarts for them. If your looking for cheaper ones head on over to eBay.
ebay amazon that are the only places i know of
Well, any selling/bidding sites like ebay gumtree and any other sites you know
You can get GIR plush toys at Hot Topic, Ebay, and Places like Craigslist! try those places, and if you don't find any, well, i don't know where else to find them.