[ Thanks to Michael for this link. ]
“When wanting to combine two or more photographs for a higher dynamic range (HDR) or correcting an overexposed photograph, I mostly use programs like Photomatix, however it is sometimes too difficult or frustrating fiddling with the settings for minutes getting nowhere. So, there is an easier way and in certain cases much better than an HDR especially if you want to avoid those really surreal photographs – Digital Blending is the way to go, you can be much more selective with your increases/decreases in dynamic range and get more realistic results
* Open your photos or photo up in GIMP
* You can do this with a single photograph, but differently exposed photos are better, they will hold more detail”