How can my partner get involved with preparing for the baby? ?

A great time. To learn more about infant safety, care and development. Encourage your partner to participate with you in childbirth classes, breastfeeding and infant nutrition classes, parenting classes and more.
Participate. Partners of a pregnant woman are entering a major period of transition too- but without the physical aspects to keep them involved, it is important to include your partner in as many provider visits as possible- especially for ultrasounds and planning with your doc/midwife. Childbirth prep class is an outstanding opportunity to learn in an non-judgemental environment.
Planning. Allow them to pick out patterns, colors, planning the room and design. Give them some choices as well.