I have been off meat for 19 years. One day I just decided that I did not want to eat animals anymore. I am ok with chicken eggs and cow milk. No animal has to be killed to give me that.
I have been off sugar in drinks for a few years now. Mainly to decrease calorie intake. But it should help with keeping teeth healthy too.
Lately, I started being off caffeine. I switched from regular to decaf coffee and I never really drank cola drinks. I am very susceptible to caffeine. I could start with one cup of coffee a day on Monday, and finish with five cups a day on Friday.
I am officially off alcohol now. Not even one beer. This is awkward in social situations, but I believe the positives outweigh the negatives.
I am trying to be off food additives and to care more about how food is produced. This one is not easy either, but I am trying to buy organic, free range, and fair trade products.
In another category, I switched from MS Windows to Mac OS for the bulk of my personal computing. No regrets here.
I am getting off Google Search as well. I set all my browsers to use duckduckgo.com for search. It is what Google was 10 years ago: simple, accurate, and beautiful.
I use Python and Ruby where feasible.
I will ditch Skype, the moment a viable alternative appears.