Torc
Torc is a newly released project (Feb 2011) that has similar goals to that of RapidSmith. As described on its web site, "Torc is an open-source C++ infrastructure and tool set for reconfigurable computing. It is suitable for custom research applications, for CAD tool development, for architecture exploration, and for any application that needs to work with real-world physical device data."
The Torc and RapidSmith projects are working synergistically to bring about high quality open source FPGA CAD tools to the research community as we frequently exchange ideas and XDL-related information.