I know that there's an article by Helen Bradley on how to create the effect in Lightroom alone and while the results look very good, I felt that it misses the part where the sharp and the blurred image are "sandwiched" as originally described by Michael Orton.
This is what I am doing with the LR/Enfuse plugin by Timothy Armes. The plugin is donationware so you can decide how much you pay for it (the free version is limited to a tiny output of just 1024px at the long side of the image). I strongly suggest that you have a look at it - as you can see, it can be used for more than just exposure blending of high contrast scenes. ;)
Once you installed LR/Enfuse successfully, the process to create the Orton Effect is actually quite simple, but it requires some experimentation with the level of overexposure and blurriness.
- Create a Virtual Copy of the photo.
- Apply 3-5 graduated filters with sharpness set to -100 all the way over the entire image* (I created a preset for Lightroom that does just that, feel free to right-click and Save-As).
- Apply something like 0.5 to 1 stop of overexposure to the now blurred image.
- In the Library grid view, select both the original and the blurred and overexposed Virtual Copy (click on the original, hold CTRL and click the copy).
- From Lightroom's "File" menu, select "Plug-in Extras" and choose "Blend exposures using LR/Enfuse".
- Leave the settings for LR/Enfuse to it's defaults and turn off the image aligning (on the second tab of LR/Enfuse).
- Wait for the process to finish :) and make final adjustments as you see fit.
"Beauty in the shade" (final image - original - blurred & overexposed overlay.)
The final image has some further adjustments via the Tone Curve (more highlights), some Fill Light to brighten the out of focus background with the delicate and muted green, and Vignette to darken the corners.
"Frosted" (final image - original - blurred & overexposed overlay.)
The frost at the rim of the leaves is quite overexposed here; you might want to be careful with the original and the blurred version, the blurry one is certainly too bright in my example, but without it being bright enough the "glow" of the effect won't be as visible.
"Swans in the Snow" (final image - original - blurred and overexposed overlay.)
This image also has additional sepia toning, slight film-grain and highlight adjustment via the Tone Curve. It was not tack-sharp to begin with (1/60s at dusk with the swans moving had them a bit blurry) but I still liked the image, and I like it even more with the soft glow of the Orton Effect applied.
*) this requires Lightroom v3 - local adjustments of sharpness in version 3 are very different from version 2 and version 1 of the software.