Since some progress was made lately, we decided to release a new set of images.
The new features available in this release are mostly camera support for the Galaxy S2, accelerometers support for the Nexus S and Galaxy S2 and RIL (telephony) improvements for all devices. A more detailed changelog is also available.
We are working to bring Replicant 4.0 support to more devices, such as the Goldelico GTA04 and the Samsung Galaxy Tab 2 (both 7.0 and 10.1 GSM versions).
You can download the images from the ReplicantImages page and find installation instructions as well as build guides on the Replicant wiki.