Getting inbound links raises your PR. Right. I try to get inbound links to my home page, in fact all external links points to the same url www.mysite.com.
The pr achieved at this moment is 3, but my internal pages are 0 (blank in google´s toolbar)... so how can I raise those pages PR? Should I ask for external sites to link to those pages instead home? That would weak my linking efforts...
Is this a fairly new site - since Google changed its ways? Why worry about the PR of those pages if you are ranking well for them. Just 8 backlinks. I'd suggest you get yourself more if possible. You are also linking off your homepage to many other sites - not necessarily a good thing. I'd assume that could be "sucking" some PR that could better be used for you internal pages.
Also try clicking onto these internal pages through a couple of ways. Sometimes PR is blank if you use your own natural internal links but shows green if you click in to it from a Google search. Experiment with accessing the pages other ways to be certain of the PR status of the moment.