One of my wall outlets seems to not be grounded?

[Mr. Coffee]

[...Some older boxes don't have a threaded hole for a ground screw...

You can usually use a clip type attachment intended for attaching an equipment grounding wire to the lip of a metal box if local regulations allow.

I just always figure that the house will probably be there 100 years or more. I try to watch out for the next owners, and the next, etc. They (and their exploring toddlers) won't know what you did or didn't do to the house wiring. That's just my practice.

[chipwitch]

[...Some older boxes don't have a threaded hole for a ground screw...

You can usually use a clip type attachment intended for attaching an equipment grounding wire to the lip of a metal box if local regulations allow.

I just always figure that the house will probably be there 100 years or more. I try to watch out for the next owners, and the next, etc. They (and their exploring toddlers) won't know what you did or didn't do to the house wiring. That's just my practice.

If your exploring toddler is servicing your receptacles, I'd say you've got bigger issues. 

At some point, given the medium, you have to choose what's really important.  Otherwise, we could have just inserted the entire NEC and instructed the OP to figure it out for himself.  I don't know who it serves more by being picayune, the OP or posters showing off their knowledge.  Ground clips can do more harm than good in the hands of a DIYer.  Is that subjective?  Yup... along with just about everything else people want to argue (like my electric mains are better than yours).  There is no such thing as 100% safe in anything.  And you can ALWAYS do things more safe than this way or that and even that is often subjective.  If the OP topic was a debate on electrical safety, such remarks would be appropriate.  Since the OP was searching for a practical solution to his problem, found it, made repairs and tested it back a couple pages ago, I'd say the medium worked.   And it is safe within a practical margin (as is EVERYTHING printed in the code book).  Besides, as far as we know, the OP used a proper ground screw attached to the box rendering your comment rather moot and off-topic.

[Mr. Coffee]

How could my post about the possible use of a grounding clip be any more moot and off topic than your previous post when you are the one that raised the issue that the OP's box may not have a threaded hole for a ground screw? I was just answering the concern. 

[chipwitch]

It was moot because he already had it done and tested.

[Mr. Coffee]

It was moot because he already had it done and tested.

My bad.