There is an excellent article on Parenting.com that has a video timeline of baby milestones over a baby's 1st year. Obviously, each baby is unique ... but these videos are great to see where a baby should/could be doing at a particular age, and what is up next!
It's amazing to watch these videos and think about Brooke at each of the stages - she will be four months old in only two weeks. We better work some more on rolling over :)
All of the videos are posted in the article, but here is a direct link to the first one (week 5) just so you can see what they are like.