Anyone wants to volunteer, we could have a fourth.

有谁想要做志愿者吗，我们就有第四个助教了。

耶鲁公开课 - 旧约导论课程节选

I volunteer in high schools and speak to them about reproductive health.

我在高中做志愿者，给他们讲生殖健康。

求职攻略 - SpeakingMax英语口语达人

Americans spend the most time out of any other people in the world volunteering in average four hours a week, volunteering outside their job which may also have a social objective more than any other people in the world.

比其他任何人所花的时间都多,平均每周有四个小时做志愿者的工作，做与自身工作无关的善事,他们比世界上其他人更具社会目标。

哈佛公开课 - 幸福课课程节选

I'm looking at doing volunteering in some service organizations,

我在寻找机会加入一些服务机构做志愿者，

再没时间也要挤出来 - SpeakingMax英语口语达人

Yes, I'm a volunteer at a couple of places.

好。我在很多地方做志愿者。

求职攻略 - SpeakingMax英语口语达人

I volunteer with an organization called "Divine Possibilities",

我在一个叫做“神圣的可能性”的组织做志愿者，

求职攻略 - SpeakingMax英语口语达人