Our brand new transitional deacon, ordained this past Saturday, wrote me an email asking clarification about those things to which he could now impart blessings. Most ordinary blessings are open to deacons, but some blessings--especially those that deal with the public cult and veneration of the Church--are not.
So I went through my trusty De Benedictionibus, an impulse buy for 41 euro when we were in Rome two summers ago, and made a list of those things a deacon can bless:
Water (i.e. "make" holy water), rosaries, holy pictures and statues destined for private veneration, medals, and personal religious articles in general. Families, couples, children, women before or after giving birth, old folks, sick folks, catechists, catechetical meetings, parish meetings, pilgrims, travelers, new homes, new schools and universities, new libraries, new hospitals, offices and shops, vehicles, technical equipment and tools, animals, fields and flocks, first fruits, and tables and meals.
Certain blessings, however, require a member of the priestly order. They include:
The blessing of a cathedra, ambo, tabernacle, of fonts and baptisteries, images of the Lord and the saints for public veneration, new church doors, bells, and organs, cemeteries, seminaries, and missionaries.