Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
I sold my 3G 8GB iPhone with all original accessories and an applied screen protector for $400.

I was pumped because it covered opening a new line to get the 16GB 3G S for $199 and the fee of $160 to cancel my old line!
 
$600 USD- 3G 16GB (BK). Yes, seriously. Although mine was an officially unlocked (HK) version.
 
White 16gig 3G craigs list $350 in less than 12 hours
it was ultrasn0wed.
 
Sold mine for $300 for 16gb black in excellent condition with an applecare warranty. I got my new 3GS 32gb for the same price so it was a straight upgrade. :)
 
Was a bit late to the party and sold my 3G 8gb for $260 on eBay. If I had listed it a week earlier I likely could have gotten closer to 300 for it
 
I sold my 2G iphone on ebay last week for £200 or $320 which i was very happy with. It was running 3.0 and was unlocked and jail broken. It was in used condition with marks on it but the screen was perfect. Getting my 3GS this week now i have got the PAC code from Vodafone.
D
 
Bought an iPhone 3g 16Gb Black on Craigslist for $290.
Met the guy in the evening outdoors.
Was hard to see the flaws evidently.
The next day it was a horror:
- cracked case
- chip off near headset
- dead pixels
- bright patch on screen

and took it to the apple store.
They replaced it no questions asked.
Sold that thing on Craigslist for $400
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.