Post to the Facebook group, Westminster Theological Seminary Student Community. This FB group, closed but to current students and their spouses, prospective students and their spouses, and current employees and their spouses, is a great way to move items within the seminary community.
Consider donating books to the Christian Literature Crusade, which ships books to developing nations. The organization's international headquarters, and drop-off point, is quite nearby in Fort Washington. They accept new or gently used Bibles and New Testaments and non-fiction Christian books, such as Bible reference, Christian living, devotionals, and kids books. See here for more info and Fort Washington drop-off address.
For baby and toddler items, please consider donating to Amnion Pregnancy Center. Such items will be put to good use by those who need them for their little ones.
New Life Thrift is a good option for other items. They give Westminster students and employees 10% off purchases! Just show your library card with your picture at check-out.
Please don't leave free goods anywhere on campus. The seminary does not have resources to be a receptacle for such items, and so the items are invariably trashed. Follow the steps above to put them to good use!