Even Sprint--which has never sold an iPhone until now-- that was originally sold by the other two wireless companies.

Want to know what makes an iPhone launch such a circus? It's not just the buyers. While crowds lined up outside Manhattan's iconic Apple Store last year to buy the then-new iPhone 4, they emerged to be greeted by dozens upon dozens of representatives from electronics resale companies, offering cash for the user's newly discarded iPhone 3GS.

You don't have to hurdle the hustle-and-bustle outside a store to get rid of your iPhone, though: There are plenty of companies willing to do the job online. Many resellers--among them , , and --will gladly pay to take your iPhone off your hands. Earlier this week, offers ranged between $160 and $314 for a 32GB iPhone 4 in good condition; don't expect those offers to last as older iPhones start flooding the resale market.

If you're wondering what it's like to sell your aging electronics to a reseller, is worth a read. It's also a good idea to do an online check-up on the companies offering to buy your iPhone to see which ones have good reputations and which have a string of unsatisfied customers. Start by checking with the . eBay, NextWorth, and YouRenew are all accredited with the organization; Gazelle is not, though the bureau hasn't recorded any complaints against that company. CashforiPhones.com isn't accredited either; its parent company, Laptop & Desktop Repair, has been the subject of 142 complaints with the bureau during the last three years.