The American Citizens Services at the Consulate in Paris has recently limited its hours and now requires that most transactions be done by mail. I thought this would be a pain, but I recently renewed a passport and it only took about a week!

For adding pages, their website says:

Passport Amendments (adding visa pages, change of legal name)

Adding visa pages to passports
This procedure must be done by mail if you live or are traveling through the Paris or Strasbourg Consular Districts. Please make sure that your passport is in good condition before having pages added to it and follow the instructions below. There is no fee for this service.

If you are traveling immediately and you have a travel ticket as proof of imminent departure, your application may be processed in person at the consular section of the embassy.

You will need to download the application form DS-19 from the following page click here, and follow the specific instructions below.

The application form (DS-19) must be completed, signed, and sent by registered mail or Chronopost with the current passport to the Consular Section of the U.S. Embassy in Paris. (See mailing address at the end of this section.)

When making this application:

* for urgent requests please send a self-addressed Chronopost return envelope,

or
* send a self-addressed registered letter envelope for the return of the passport (lettre recommandée; "destinataire / expéditeur" information must be completed on the form) with correct postage = 4 Euros postage for "sans avis de réception" return by mail or 4.50 Euros for "avec avis de réception" return by mail.

*****
The forms and more information can be found at:
http://www.amb-usa.fr/CONSUL/oas_pptamd.htm

I have always added inserts (I have a total of 5 in my current passport) from US Consulates abroad, 2x in Sofia, 2x Hong Kong and 1x Singapore. All occasions the process was quick and painless. In and out of the consulates/embassy in less than 15 minutes. The last time was in SIN about 3 or 4 months ago and I was in and out in 10 minutes...

I too have added pages while overseas which based on the general discussions seems to be the way to go (especially if you are there anyway). My experience in the Singapore consular section was quick, efficient and the whole process took about 15 minutes. Try to minimize what you bring to the consulate because this will complicate the security screening and you will have to leave the items with security anyway.

A few months ago I did exactly this. I visited the American Consulate in Paris (note: not the US Embassy, the other bldg 2 blocks away), and they added pages to my passport on the spot. It took all of 5 minutes. Perhaps they changed their policy only very recently, per Louie_LI's post, but they made no mention of a process by mail requirement.