Here's a quick & dirty tool I put together for Outlook to be able to update all the phone numbers of contacts to make them E.164 compliant. It relates back to a post a while back around the challenges of formatting numbers 'correctly', particularly important once you get into using click-to-dial technologies such as Office Communication Server.
The tool itself is basic since it's only really expected that people will run it once, to sort out the numbers of old contacts you might have. It will check all the contacts in a given folder and automatically fix the numbers up, but there are a few caveats...
A final word: this is completely unsupported, supplied "as is" etc. If it does mangle all your contacts up, just revert to your backup copy - and if you didn't take a backup then you've only got yourself to blame.
Harsh but fair I think :)
The logic converts "from" the format on the left to the format on the right... (_ denotes a space)