OpenBSD/sparc64 runs on the 64bit Sun UltraSPARC machines. The current port maintainer is Jason Wright (jason@openbsd.org). Others are welcome to contribute.
The orginial port was made for NetBSD by Eduardo Horvath and released for the first time in January 1999. The porting to OpenBSD started in August 2001 and in the end of September the first binary snapshot was released. The porting was done mainly by Jason Wright and Artur Grabowski and was done on both sbus and PCI machines so that a decently wide hardware support was ready even before the system could boot multiuser.
Currently most of the hardware available to the developers boots multiuser and supports enough of the on-board devices to be generally useable. No attempts have been made for graphics console support yet so only serial or prom consoles are available. The same applies to support of more expansion hardware for the PCI bus or the SBUS.
There hasn't been a need for a separate mailing list for OpenBSD/sparc64, instead the OpenBSD/sparc mailing list is used. To join the OpenBSD/sparc mailing list, send a message body of "subscribe sparc" to majordomo@OpenBSD.org.
There has not been any formal release of OpenBSD/sparc64 yet, but more or less functional snapshots are made quite often and can be found at: ftp://ftp.openbsd.org/pub/OpenBSD/snapshots/sparc64/