Other than jailbreaking, I think there are a couple of methods.
1) If you fill up your pages with apps, but still have storage space for more, they should load on the iPhone but only be available using Spotlight to search for them. So fill up on 'visible' apps, then install the ones you want to hide.
2) This was inadvertent. My mom even stumped an Apple Genius the other day, when they were looking for the Notes app.
I had upgraded and gave my original iPhone to my mom ("Happy Mother's Day... here's something I don't want anymore"). Anyway, I deleted apps she wouldn't be interested in, and the result was several blank pages. The 'Notes' app, which the 'Genius' was looking for, was on the last page.
So, they saw a few apps on the home page, scrolled to the right and saw a blank page, and gave up, assuming the Notes icon was AWOL.
So, load up enough apps to have several pages, move the desired apps to the back, then delete the apps in between to create blank pages. I would have thought the blank pages would disappear (I think they do in the Simulator) but they didn't.