Is there a way to sort by the various columns you see in the thread listings? Such as sorting by the threads I've posted in?

far left hand side, there's an icon on every thread.
one means you have posted in that thread.
otherwise there are some sorting options on the lower right hand corner of the board you are posting in.
and on the lower left hand corner of the board, there's a description of the icons.

You can also click on your name and then click "find member topics" in the drop down menu that appears.