сойти с ума

1) General subject: be off one's pannikin, go bughouse, go bugs, go loco, go mad, go off one's chump, go out of one's head, go round the bend, heat, lose mind, lose one's reason, lose reason, lose senses, run mad, to be off (one's) pannikin, be off pannikin, go off head, go out of mind, become insane, go off one's head, take leave of one's senses, (рехнуться) mess with one's mind

2) Colloquial: be out to lunch ('If I were you, I would not talk to William. He is out to lunch, you know.'), cook rabbit (did she cooked your rabbit? - что, она еще не совсем с ума сошла?), take leave of senses, be out of (one's) senses

3) Rare: mad

4) Rude: go off nut

5) Jargon: blow top, blowone's top, lose (one's) wig, go zonkers (What a day! I almost went zonkers. Что за день! Я почти сошёл с ума.), go postal (http://en.wikipedia.org/wiki/Patrick_Sherrill), lose (all) one's marbles, flip wig, go off the deep end, flip over, go bonkers

6) Makarov: become demented, become deranged, become mentally deranged, go crazy, go mental, go off (one's) head, go off (one's) nut, go off the hooks, go out of (one's) mind, go out of (one's) senses, lose (one's) senses, take leave of (one's) senses

7) Taboo: crap out, poop out