Besides zazen, my favorite Buddhist practice is a more traditional one: the practice of the brahma-viharas.
The four brahma-viharas ("Abodes of the Gods") are:
-Equanimity (composure, patience, evenness of mind)
-Sympathetic joy (vibing off of other people's happiness)
-Loving-kindness (gentleness, openness of heart to all sentient beings)
-Compassion (being aware of and moved by the suffering of sentient beings)
The Pali terms for these are upekkha (equanimity), mudita (sympathetic joy), metta (loving kindness), and karuna (compassion).
I don't have a particular concrete practice for cultivating the brahma-viharas; rather, I notice that they are signposts of effective practice in general. Zazen promotes these qualities, as do many other traditional Buddhist practices. However, a basic form of practicing with them is, noting their arising, I try to see what led their arising; noting the arising of their opposite qualities (vindictiveness, selfishness, jealousy, irritation, etc.), I try to see what led to the arising of these opposite qualities.
I like putting myself in situations that tend to draw out qualities that oppose the brahma-viharas and working to transform my state of mind in these situations to one in which the brahma-viharas naturally arise instead. I find that the first step is usually promoting tolerance or patience (which I would identify with upekkha). If something bugs me, I try to watch my mind as it gets "bugged" and identify the mental events that lead to this state of mind. Over time, I can often identify what's going on and change how I react in these situations.
I also find that these qualities naturally arise in moments of surrender, often after some painful experience. Letting go of the self, letting myself surrender to disappointment, instead of fighting or trying to hold on, I find that one or more of the brahma-viharas often accompany the experience of sadness and defeat. When you're not trying to defend the self, sadness is a tenderness of heart that promotes kindness. I find that cultivating these qualities of mind has much more of a profound impact on how I interact with others on a day-to-day basis than cultivating non-distractedness of mind. But of course all of this rests on the foundation of a good zazen practice, without which the ability and reflex to watch what's going on in the mind without identifying with it becomes much more difficult, if not impossible.