The iphone/ipod touch only hold 9 pages of apps, but does include the home page with the clock, calender, app store, itunes, etc.
Actually - you can store as many apps as you have space for (there may be a limit, but I've never reached it) but you'll only ever see the first nine pages unless you use the search function in the 3.0 OS (which is awesome, by the way!) I really wish I could remove (or "turn off" ala Nike+iPod) some of the default apps that I don't use...
In the 3.0 OS you can have 11 pages but as people have said before you can still put apps on after that, they just won't show up on the page. You can of course search for them which means you can have as many apps as you want (to an extent).
Try checking out an app for free called "Categories". You can put all those pesky games / apps /etc into folders and sub route the first 1/2 pages
Categories only works for jailbroken iDevices I believe. I would otherwise be all over it. Actually the methodology (or lack thereof) of the springboard is my biggest reason to consider jailbreaking. I thought that the Apple was supposed to me user friendly... Having programs that are hidden - so you have to remember they are hidden, and you have to remember their names - it makes the hardest "memory training game" easy by comparison...