Believe it or not, there are some older iPhones still in use out there, and they're not going away anytime soon. Sure, Apple would prefer you to upgrade your device to the latest and greatest models, which are compatible with iOS 5. Those models include all of the following:
If you still have your trusty iPhone 3G or the original iPhone, then you're out of luck for running iOS 5 on your device. But the folks over at Whited00r have changed that. They've created a software distribution that has most of the iOS 5 features, and will work on the original iPhone, iPhone 3G, and first and second generations of iPod touch. Check out the demonstration below, pitting an iPhone 3G running Whited00r's software versus iPhone 3GS running Apple's iOS 5.
Not too shabby, eh?
Whited00r has included low-memory multitasking, similar home screen, folders, reminders, iCloud integration and more. It's also includes Cydia. So, there's no need to update your device anymore. Keep it cheap with this custom jailbreak iOS 5 update (that is obviously... free).
To update your old iPhone or iPod touch to iOS 5 through Whited00r, just download the software and go to their installation page to see how it's done. By now, anyone who has an older device should already be familiar with jailbreaking, so it shouldn't be too much trouble to figure out.