Thank you guys for the HDR pointers and tips. I was too lazy to go anywhere, so I shot some raw images from my back porch on a tripod (w/ the delay on, to reduce tripod shake), and made my first exr file.... (it's at bradfitz.com/exr/backyard.exr if you want it, not linked because it's 18MB)
Here's a tone-mapped version of that exr file:
That was all done with Photomatix Pro on my Mac. Next up I'll play with the various tools on Linux, using the same raw files and same openexr file.