Apple devices age well, so well that there are still people using the original iPhone and the iPhone 3G. When we think of those phones, we think "classic hardware with older software," but it doesn't have to be that way. For Apple fans with these now classic handsets, there's whited00r, a version of iOS that mimics some of the features of iOS 5. It's been around as a release candidate and finally made it to a stable release.
Whited00r is based on iOS 3.1.3 and has mods that let you experience folders, multi-tasking, iCloud-like functionality via Dropbox, reminders and more. Whited00r doesn't include notifications or iCloud, but there are third-party work arounds. It also doesn't support the App Store, but you can install Cydia or access the App Store using a Safari bookmark. Yes, it's not iOS 5, but it's the closest you will get on your older handsets.
You can find download and installation instructions on whited00r's website. The process is very straightforward, especially if you already know how to install an ipsw file using iTunes.