Edit:
We have now a temporary git repository at gitorious:
http://gitorious.org/replicant
Build process:
Let's say that our build directory is ~/replicant
* Add that file:
{{{
TARGET_PRODUCT := htc_dream
}}}
To ~/replicant/buildspec.mk
* Then type
{{{
cd ~/replicant
export ANDROID_JAVA_HOME=$JAVA_HOME
make
}}}
* The files to flash are in ~/replicant/out/target/product/dream,flash them and then clear the cache
* boot and push the wifi firmware if you want it