I was already pretty impressed by the eBay app for iPhones, but these two new apps for either sellers or those who want to buy/sell locally are worthy additions to your home screen. Particularly that Craigslist replacement-sounding Classifieds one.
It remembers your location and will only display items near you based on what you're looking to buy, thanks to the iPhone's GPS.
The second app—also free—has been described by eBay as a "power tool" so the item being sold can be listed in under 60 seconds. You better have good lighting, because otherwise those iPhone pictures won't do that rare vinyl any justice at all. [eBay Selling app, eBay Classifieds app]