Well other than Giving away free content(with your inlinks ofcourse), you can write for others. This may not apply for all the niches but say if you are a marketer or SEO than it does helps you to establish yourself and get some clients.
Anyway coming back to "Writing for others", Go to webmaster forums and start looking for possible blog owners.

Tip – There is a service called http://www.reviewback.com/ which can be used to find blog review partners. I haven’t used it before but the fact that its there for more than a year means it must be working for few. So explore it and find a person, pay him some money to act as your representative and give him access to your blogs. The rest is self explanatory.