Here are links to places where I have found many of my most interesting coins (I am not paid for any of these links; I actually patronize these businesses):
Joel Anderson
Digga from Dover
"Anything Anywhere," with a HUGE number of worldwide coins and banknotes, well priced.
DNE Coins, with a great selection of unusual world coins and tokens, and an attribution service.
This is a site that seems to have the best prices for supplies:
Brent-Kreuger Coin Supply
Here are people with whom I have traded coins successfully:
Alex Pathfinder's
Coin Trading Club (Japan)
Daniel Colombres Wohlenberg's Coins and Banknotes (Mexico)
Denis Buric's huge list of duplicates are here (Croatia)
Borislav Atyashkin who has a large list of Soviet commemoratives(Germany)
Dzmitry Hulecki (Belarus)
Cedric Sauvage's home page (France)
Izidor Dolenc, who has lots of modern Polish commemmoratives (Poland)
Adomas Putrimas, who has many Baltic coins, including pre-WW II silver (Lithuania)
Stas Klyich (Israel)
Aldo Martins (Portugal)
Georgios Kollidas (Greece)
Misha Kolot (Israel)
Ihssan Hassan, many Middle Eastern coins, banknotes, and others (Iraq)(x2)
Bob Hicks, Texas, USA (My first trade with someone in the US!)
Joao Augusto Mano Araujo (Portugal)
Lisjak Slobodan (Serbia)
Enrique Waizel (Canada)
Tiffany Gerulis (Northern Ireland)
and now USA (x2)
My good friend
Jesús Méndez Moscoso (Spain)
Alexandre Teixeira (Portugal)(x2)
Vincent Pidansat (France)
Clemens Weykamp (Netherlands)
Davide Paglionico (Italy)
Daham Perera (Sri Lanka)
Juan Pettiti (Argentina)
I regret that I have had a recent bad trade, with Ciro Bevilaqua from Brazil. I sent him coins in mid-November 2007, have received nothing back, and have not received any replies to my e-mails since then.
I had one good trade with Aleks Shoty from Israel, and one other trade where my coins disappeared in the mail, and nothing was sent from him. I hesitate naming him here, except that he also appears on other bad trader lists, so I advise caution.
I recommend that anyone who wishes to make a trade should Google that person's name first - there are enough "Bad Traders" lists out there to smoke out most offenders. Their numbers are thankfully few.
Ron Wise's World Paper
Money Page is the best site for finding worldwide paper money images:
The American Currency Exhibit is an outstanding source for US currency images. In addition to the "Showcase" be sure to click on the "Index of Bills" to see just about anything.
Don's World Coin Gallery for finding images of 10000+ coins, including Krause numbers and value approximations:
Dan's Coins
is a good coin image site, with values, Hejira, Israeli and Thai date information, and much more: