Why am I doing this? *sighs*
Lurk. Read threads; every few seconds, if you click to another page or part of the site, you can gain a couple gold.
Sponsor links are here. Only two work, but it's a quick 40-50 gold a day (Note: wait a couple minutes between clicking the links to get the most gold).
Polls. Each poll will give you 10 gold. You must wait 30 seconds between polls in order to get the 10 gold. You can also get 5 gold for creating a poll.
Posting. See Emerel's response, above. Also, if you find a discussion you like, and read/contribute to it, you can find yourself racking up some gold.
Selling stuff in the Marketplace and Exchange. Those places have FAQs. Read them.