Find empty files: find . -size 0
Files greater than 700M: (does not fit CDROM) find . -size +700M
Find exactly files with 'mode': find . -perm mode
Find files with all bits of 'mode' set: find . -perm -mode find . -perm a+x
Find files which are readable (maybe acls or NFS mounts make this impossible):
find . -readable find . -writable find . -executable