Hi.  The new version of tme, 0.4, can now emulate a Sun 3/150 system
with an si SCSI host adapter and both the onboard bwtwo and a VME cgthree.
NetBSD 1.6.x seems to run pretty well, with X also (two-headed, even).

However, please remember that tme comes with no warranty.  Don't
trust it to do anything correctly.

  In particular, do not trust tme for floating-point work.  The
  m68881 emulation is the least tested part of tme.

Instructions on how to download, build, and use it (including some
screenshots) are at:

http://theory.lcs.mit.edu/~fredette/tme/index.html

The emulator was developed on a NetBSD/i386 1.5 machine, but I've also
compiled and tested it a little on NetBSD/sparc 1.6, FreeBSD/i386 4.8, 
and SuSE Linux i386 8.2 (kernel 2.4.20).

The code is still rough and the distribution isn't too user-friendly, but
if you follow the instructions carefully, and have experience installing
NetBSD on Sun 3 machines, you just might end up with an emulated Sun 3.

-- 
Matt Fredette