To correct
hackthemainframe's writeup, the latest major version is R5 and was released in March 2000.
Updates have brought it to 5.0.3. There is a Personal Edition available which can boot from an image file on a
fat32 or
ext2 partition, or can be installed to its own partition after
booting.
http://free.be.com
There'll be hardware OpenGL and decent networking and the Java 2 VM soon. When it's done... really... sure... yeah.
Edit, June 10, 2002: Well, that didn't work out too well, Be's been dead since January and the entire be.com domain is gone, and for sale for several hundred thousand dollars. BeOS 5 Personal Edition is still available from mirrors, listed on www.bebits.com.