There's not an easy path to it yet, but the firmware is on Apple's servers, MacRumors.com reported Thursday.
The iPhone 2.0 software allows existing iPhone and iPod Touch owners to have access to the software features that will be available on the new iPhone 3G that hits stores Friday morning (but not to the hardware upgrades, which include 3G Internet access and GPS). This means not only the 500+ third-party applications already in the iPhone App Store, but also support for Microsoft Exchange ActiveSync.
Third-party applications range from games and electronic books to iPhone versions of big social networks like MySpace and Facebook. Facebook and MySpace's iPhone applications will let users seamlessly upload photos to albums on the social networks, and Facebook's will let members with location-aware iPhone 3G devices see which of their friends are nearby.