Being a native English speaker has had its advantages and disadvantages abroad. I have found that, although never a part of my job description, I am often the go-to person for anything that has to do with English, which can be fun. I edit emails that will be sent to many people; I edit content for internal magazines; I edit websites and brochures; and much more.
I have also done some voice work. At my school (while working at the Career Center), I recorded some online podcasts, etc. At my current company, I just did the English voice-over for an online commercial for a Lego backpack for children - which is pretty fun.
I am also making some extra cash on the side by editing students papers. I charge a fairly nominal fee, but it is tax-free money, in my pocket. Once I get a 'client', they are loyal for the tenure of their education. I just recently finished editing a 100-plus Master's thesis for two Danish guys, who then spread the word to their friends, and I am lined up with one more already. This is something I can do fairly easily at night, while I am watching tv, etc.
I recently began writing for a magazine that is geared towards international in Denmark called Insight. I got paid a decent fee per article that I write, so that has allowed me to brush off my journalism skills again, which has been fun.
I definitely feel the need for these services, especially within non-native speaking international companies. With a business plan, some work and marketing, it is possible that editing and cleaning up internal and external documents could provide a living for someone if they were interested. Something for me to think about.