You can submit your for-sale items here. I have yet to figure out the terms and conditions, such as how long to keep the ad there (if its not sold in xxx months, then probably no one wants it).
But I have one request. HTML formatting is difficult so please don't give me strangely formatted ads and expect me to convert it to html (UNLESS its full formatted in HTML by yourself :)) Ideally, it should be like the newspapers - text blocks eg:
NAD 312 integrated amplifier (purple colour) for sale. Bought $999. Selling $333. 1 year old. What Hi-Fi 10 stars, Hi-Fi Choice Super-highly recommended. Owner only listened to Teresa Teng. No hard rock. E-mail email@example.com.
To make your sale more attractive, seller can/should mention:
I don't really have much experience in this. While I was in a Hostel, I did sell my Dad's Mission Speakers for $100 by posting on the university BBS (they cost $400 new, so I sold it in 1 day).