People mainly sell their in-game WoW currency vs forum gold, whereas in Diablo 2 you sell items, so in that respect it's a little different from Diablo 2. But yes, you can spend your forum gold by trading other users who offer WoW items and in-game gold.
Since you're from Colorado I assume you play on US Servers ->
Trading - US Servers.
Remember to check the
World Of Warcraft Trading Rules 