I sometimes find myself wasting time on the computer, or watching movies when I have work to do. What I do then is swear in Allah's name that until a task is done (some tasks take a few months) that I won't waste my time doing these things. It used to work perfectly; however, I don't know how I started breaking these promises, but I did and I want to know: what's the consequence? I think I heard somewhere that you have to fast three days or something, but I figured I would come here and get a clearer answer.
The compensation/expiation of breaking an oath is clearly stated in this ayah of the Holy Qur'an.
Allah will not impose blame upon you for what is meaningless in your oaths, but He will impose blame upon you for [breaking] what you intended of oaths. So its expiation is the feeding of ten needy people from the average of that which you feed your [own] families or clothing them or the freeing of a slave. But whoever cannot find [or afford it] - then a fast of three days [is required]. That is the expiation for oaths when you have sworn. But guard your oaths. Thus does Allah make clear to you His verses that you may be grateful.
It is not acceptable of a muslim to break promises all the time.
Sahih al-Bukhari :: Book 1 :: Volume 2 :: Hadith 32
(and many similar ahadith)
Narrated by Abu Huraira:
The Prophet said, "The signs of a hypocrite are three:
Whenever he speaks, he tells a lie.
Whenever he promises, he always breaks it (his promise).
If you trust him, he proves to be dishonest. (If you keep something as a trust with him, he will not return it.)"