Listing your old crap on eBay is already much easier using an app than using eBay's website, but the eBay Instant Sale app goes one step further—at least, with old gadgets anyway.
All you have to do is search for the gadget you're selling, and eBay will make you an offer. If you accept, you're basically selling your old electronics to a reseller, so while the price might not be as high as you'd get otherwise, it's got to be the fastest and easiest way to clear out that bottom drawer.
eBay will then send you a free shipping label to print off, which you attach to a parcel and send on to the reseller. When they're convinced it's in good nick, you'll be credited with the cash in five days. And if you're trying to flog a scratched-up Creative Zen MP3 player from eight years ago? They'll recycle it for you, for free. [iTunes via App Advice]