Meditations by Marcus Aurelius is a great straight-forward read and seems to be considered the gold standard on the subject.
Dreyfus has made important and influential critiques of "cognitivist" AI grounded in Heideggerian arguments... which can be a fascinating angle to approach existentialism for computer scientists.
I gladly recommend bringing a book of philosophy while travelling. You get new impressions to somehow apply ideas to, which gives a new depth to the travels and the book... plus you might form some interesting associations.
I read this Dreyfus Heidegger book a lot during a stay in rural Thailand, and I had lots of time to reflect... And, for example, part of the book is about this background of cultural habits that we rely on daily, and that only manifests consciously when it turns unfamiliar—like when in a foreign culture. So that was fun to think about.
Yeah, a relaxing vacation mixed with the mental stimulation of good philosophy—add a cup of coffee and that's heaven...
Rule a nation with justice.
Wage war with surprise moves.
Become master of the universe without striving.
How do I know that this is so?
Because of this!
The more laws and restrictions there are,
The poorer people become.
The sharper men's weapons,
The more trouble in the land.
The more ingenious and clever men are,
The more strange things happen.
The more rules and regulations,
The more thieves and robbers.
Therefore the sage says:
I take no action and people are reformed.
I enjoy peace and people become honest.
I do nothing and people become rich.
I have no desires and people return to the good and simple life.
Some of social philosophy essays I have read recently are:
Konrad Paul Liessmann - theory of ignorance: the errors of the knowledge society (original: Theorie der Unbildung: die Irrtümer der Wissensgesellschaft, 2006 )
Elias Canetti - Crowds and Power (original: Masse und Macht, 1960)
Georg Simmel - Philosophy of Money (original: Philosophie des Geldes, 1900)
edit: formatting
If you are a person who like to do things instead of just reading about them, philosophy will offer you a whole new way of thinking about what you do.
I have always tried to strike the balance between thinking and doing. I.e. reflect on what I am doing.
Each to their own of course, but I can't recommend philosophy enough as long as you are able to apply it to some extent.
Richard Dawkins, Daniel Dennett, Douglas Hofstadter, Marvin Minsky, Tsai Chih Chung, Alan Watts.
Pick up anything by any of these guys and you'll be off to the races.
http://www.philosophizethis.org/
Start at episode 1 and work your way up. It improves a lot around podcast 12 or 13 as the speaker finds his stride.
Bertrand Russell has also written a highly regarded introduction, though I haven't read it.
Ironically it put me off of philosophy somewhat. I left it with the impression that a worryingly large number of philosophical questions were either tautological or just very clever word play.