From Snow Leopard 10.6.0 Install DVD:
(For all files, frameworks, etc that are compatible - not listed - I copied them over to the current Snow Leopard/PPC developer image in the appropriate places as well as the Snow Leopard 10.6.0 mach_kernel...)

/usr/bin
Awk - not ppc compatible
Split - not ppc compatible
update_dyld_shared_cache - not ppc compatible
Wc - not ppc compatible
Stat - not ppc compatible
sw_vers - not ppc compatible
Sed - not ppc compatible
Touch - not ppc compatible
hdid - not ppc compatible
Hdiutil - not ppc compatible
Head - not ppc compatible
Security - not ppc compatible
Sandbox-exec - not ppc compatible
Notifyutil - not ppc compatible
Grep - not ppc compatible
Ditto - not ppc compatible
Mkfifo - not ppc compatible
Mdimport - not ppc compatible
cksum - not ppc compatible

/usr/sbin
AppleFileServer - not ppc compatible
BootCacheControl - not ppc compatible
KernelEventAgent - not ppc compatible
Chown - not ppc compatible
Coreaudiod - not ppc compatible
Disktool - not ppc compatible
GPT - not ppc compatible
hdik - not ppc compatible
ioreg - not ppc compatible
Kextcache - not ppc compatible
lsof - not ppc compatible
notifyd - not ppc compatible
pdisk
Portmap
Raidutil
Securityd
Syslogd

/usr/libexec
kextd
Hidd
repair_packages
Sandboxd

/usr/lib
Libsandybox.dlyb
libsandbox.1.dlyb
liblber.dylib
Libldap.dylib
libldap_r.dylib
Libkrb4.dylib
Libk5crypto.dylib
Libkrb5.dylib
Libkrb524.dylib
Libkrb5support.dylib
libgssapi_krb5.dylib
libdtrace.dylib
libIOkit.dylib
libIOKit.A.dylib
libAPSimple.dylib

/System/Library/Extensions
ALL BAD

/System/Library/Frameworks
OpenCL

/System/Library/PrivateFrameworks
CoreRAID.framework
GraphicsAppSupport.framework