Overland is always looking for nonfiction pieces, especially for their online magazine. Each week or so, they list particular subjects that seem interesting on their pitch page, though they consider pitches on any topics.
Their online magazine will begin publishing again from 16 January 2017. If you're thinking of pitching or writing something, check out their pitch page for the topics that are of interest here.
As of January 2017, they will be paying $120 for online articles.
Overland also accepts pitches on any other topic. You can pitch at any time.