Amark.com is a popular precious metals marketplace that allows users to buy and sell silver, gold, and platinum bullion. This site has been around forever, it was launched back in 1996, and has been fairly active ever since.
A-Mark also has a really useful front page. On the main page they display current prices of popular gold coins, gold bullion, popular silver coins, silver bullion, bags of 40% silver, bags of 90% silver, and platinum coins and bars. Also displayed is the forex/currency exchange rate changes, and the DJIA, & S&P 500. Content on the main page refreshes every minute or so automatically so you can be certain what they show is accurate.
We’ve never ordered from A-Mark, but have shopped around their online store. The content is fairly reasonable, but the selection is not huge. All in all a good resource.