Quran
Quran (16:106) - Establishes that there are circumstances that can "compel" a Muslim to tell a lie.
Quran (3:28) - This verse instructs believers not to take those outside the faith as friends, unless it is to "guard themselves" against danger, meaning that there are times when a Muslim may appear friendly to non-Muslims, even though they should not feel friendly.
Quran (9:3) - "...Allah and His Messenger are free from liability to the idolaters..." The dissolution of oaths is with pagans who remained at Mecca following its capture. They did nothing wrong, but were evicted anyway. (The next verse refers only to those who have a personal agreement with Muhammad as individuals - see Ibn Kathir vol 4, p 49)
Quran (66:2) - "Allah has already ordained for you the dissolution of your oaths..." For today's reader, the circumstances for betraying your word are not specified, leaving this verse open to interpretation. According to Yusuf Ali in his commentary: "if your vows prevent you from doing good, or acting rightly, or making peace between persons, you should expiate the vow." (Presumably, whatever advances the cause of Islam would qualify as 'doing good').
Quran (40:28) - A man is introduced as a believer, but one who had to "hide his faith" among those who are not believers.
Quran (2:225) - "Allah will not call you to account for thoughtlessness in your oaths, but for the intention in your hearts" (see also 5:89)
Quran (3:54) - "And they (the disbelievers) schemed, and Allah schemed (against them): and Allah is the best of schemers." The Arabic word used here for scheme (or plot) is makara, which means 'cunning,' 'guile' and 'deceit'. If Allah is supremely deceitful toward unbelievers, then there is little basis for denying that Muslims are allowed to do the same. (See also 8:30 and 10:21)