Would it not be better this way:

for (i = 0; i < 1000; i++)

     printf ("%d %d %d\n", i / 100, (i % 100) / 10, i % 10);

IMHO, such patterns (multiple nesting with empty outer loops), in most cases, are really an indication of just one real loop. Using multiple counters might also be an option.

In case the loops are doing something different, they should be indented separately. For instance, the following makes little sense:

for (i = 0; i < 10; i++) {

foo (i);

for (j = 0; j < 10; j++) {

     foo (i + j);

for (k = 0; k < 10; k++) {

foo (i + j + k);

}

}

}