Recycle of course! Side the doghouse! Arts and crafts. Wood siding is unique though in its beveled design which makes it difficult to use it (in my mind) for anything but layering horizontally on a vertical flat surface.

Also check if there are any building material re-use places around. Here in Portland we have the ReBuilding Center, which is a non-profit house part recycling store. I buy many house parts for my house and bits of old house for art projects (old single pane windows are great stained glass mosaic backers for $5-10 a pop, old tile, etc.)

If nothing else, you could also check for building material recycling places that grind up old wood and compost it rather than tossing it in a landfill.

Good luck!

I used some to edge garden beds--worked great!