Iphone Dev Center today released the latest sdk for iphone 2.2.1 which can be downloaded from below.
iPhone SDK for iPhone OS 2.2.1 is an update and bug fix release to the iPhone OS
developer tools. This release includes new, optional GCC and LLVM compilers,
updated project assistant, a simplified toolbar, and additional security enhancements.
The iPhone SDK includes the complete Xcode 3.1.2 developer tools for Mac OS X
development as well as the SDK components for iPhone OS development.
We encourage developers to apply to the iPhone Developer Program for access to
additional support resources, as well as provisioning resources to enable
development directly on an iPhone or iPod touch.