I used PowerPoint to make a pregnancy book with lots of info about how things went, classes I took, books I read, wieght gain, doctors visits, sonograms, etc. I put that in little plastic pockets in a duo-tang. I made it to look a bit like a scrapbook with pictures printed and stuff.
As for after Simon's birth, I keep writing the "firsts" and great stuff on the calendar we keep on the fridge. Then, once a month, I sit down and go through my baby book to recopy it all. I find it easy to keep doing this way.
I have seen some books that go on 'til 12 years old or so as they use each new school year as a base but expand to family as well. I think I may get that too!
P.S. When I do stuff on computer, I save it on a cd/dvd presuming Simon will be able to keep it for a long time this way!