By the help of software app namely Whited00r 5.1, you are able to install iOS 5 from iTunes to your old devices. This app utilizes an unofficial iOS 5'S custom version that can be operated to all iPhone versions -- except its first generation and all iPod touch types.
Once you managed installing iOS 5 to your iPhone 2g, 3g or iPod 1G and 2g, they can perform multitasking, having reminders, homescreen folders and then newsstand, of course increasing their performance speed.
Last but not least, you will get a hacked version of Apple's iCloud service that utilizes Dropbox storage to stores your photograph, media and more features can be seen through their changelog here.
Whited00r is a free sofware, you can download and install it if you like from their website. But remember this one is a custom operating system and unofficial too, that could have potential security issues to your device.