I'm not exactly sure what you mean by targetted at the developer, but all of the source code (inc. eclipse project files) is available with each release. Also, a nightly build is available which contains up-to-date check-ins, but not necessarily fully qa'd. Developer documentation is available on the WIKI (inc. API docs - although still in development).
If you require something extra, please let us know.
i saw in the road map "After release of our version 1.0, we will provide a release targeted at developers, which includes features that will make it easier for the community to extend the Alfresco platform"
" Documentation and Examples - Documentation of building different types of applications, extending the web interface, template examples and adding new services. "