Invite people over for weekends. When my kids were babies I was working (still am), so I would just have people over on the weekend. Brunch, lunch, whatever.
Meet friends for a walk with the stroller.
Meet at a park mid-week if you are able.
Look for new-parent groups. The vast majority of my long-time friends came from our new-parent groups. The stay at home moms would get together mid-week at parks, but we always schedule things on weekends too. Park, lunch, coffee, walks. Sometimes we do "mom's night" - dinner and a movie, dad is home with the kiddos. Dads do dad's night out too.
Also, note that when your kid starts preschool or elementary = instant new group of friends, especially if you volunteer at the school in any way, shape or form.