(1) sometimes 副词= 有时候; "at time; now and then"
(a) Sometimes she wished she were back in Beijing;
(b) Sometimes her photography is breathtaking;
(c) Sometimes they come for a month; at other times for six months"
(2) sometime 副词= 某时:"some day; one day"
(a) I will see you sometime next week: 我下周某时/某日会见你
(b) Let's get together sometime.
(c) Why don't you come and see me sometime?
(3) sometime 形容词:
(a) Bush was sometime the U.S. President 某个时候=<前>总统.
(b) She was in her early thirties, a sometime actress, dancer and singer. 某个时候/时代是演员, 舞蹈家，歌手.
(4) some time 名词短语=一段时间
(a) Please give him some time to finish his homework.
(b) I have not met my parents for some time already.参考资料：
http://zhidao.baidu.com/question/569233