Our group uses contents from ResearchCyc and OpenCyc in almost all of our projects. That is, we use our own reasoning engine, running with knowledge extracted semi-automatically from a Cyc KB. While reasoning engines are fine for many purposes, we find it useful to build our own reasoning engine, optimized for our purposes.
We think that these KB contents are a valuable resource for the AI research community. To obtain ResearchCyc, you need to contact Cycorp for an appropriate license. OpenCyc, on the other hand, is licensed in a way that allows redistribution. Consequently, it is OpenCyc contents we use in projects such as CogSketch, where we freely distribute our system.
To facilitate experimentation with OpenCyc, we have made available the contents we have extracted from it here. Additional resources may be posted here in the future. Enjoy!