I've been out of dental technology for over 10 years now, but yes i've seen Amalgam
used in root canals. Heck, i've even seen part of a tooth reconstructed from amalgam.
As far as metals used for posts, high content gold is considered the best but palladium and even mixture of gold & platinum come to mind as well.
All metals used in dental technology are alloys combined of more than one metal except for titanium which is used for implants. So when i say gold, i mean an alloy that has gold in it.
In the 90's, most dentists preferred palladium for their crowns and bridges and high content gold for post construction. Palladium costs less than gold and is as biocompatible, but it is more rigid than gold which may not be suitable for some applications.
All that said, there are many dentists who order everything in non-precious metal for cost effectiveness which can be as bad as amalgam. Non-precious metal almost always has nickel, beryllium, probably some copper and a few unknown crap but costs about 20-30 times less than a decent quality gold alloy.
Usually the lab includes a sticker with their lab work which details exactly what is in the alloy, so if you're concerned, you should ask your dentist for this sticker.