http://www.bullionstacker.com/ - Join a precious metal forum!
http://www.coinflation.com/ - Check out Coinflation for the melting values of common coins.
Suppose you're buying from a pawn shop or local coin dealer, don't get ripped off! Measure the bullion or coin you are buying with an inexpenseive jewlery scale ($10-$20 on ebay!).
Morgan and Peace Dollars
= 26.73grams
Eagle Dollar = 31.1grams
There's lots more information I'll add later, but this is a start!