I've only done things with gofreebies.com but I know there are a lot of other things. When I was pregnant with my first I was talking in line with a lady who worked for a research place that gave out free samples in turn for doing surveys for the stuff. They say to sign up early (before the baby's born) because there is such strong interest. The one we thought about doing was free diapers (They actually provided ALL diapers for a specific amount of time, but they had to be there diapers, you couldn't pick etc). We decided not to because of where the place was located. Try asking your DR if they know of other things like that if your interested.
I would just google Samples for Mum to be's and things like that!!...im not sure where you come from so its hard to say!!....really most things ask u to sign up to there sites if your willing to sign up then theres quite alot out there to get samples frm! =]