Since I posted the Export Layers script, a few people have asked me to add an option to export at a higher resolution. There is no DPI export option listed in the Adobe scripting guide, so it didn't seem likely to happen.
Yesterday, however, I received an email from Mike Moreau Jr. at HarvestMedia, who pointed out that there was an option to scale exported images. Aaaannd, shortly thereafter, I added scaling sliders to the scripts UI.
If you need an image exported at, say, 300dpi, just calculate (desiredResolution/currentResolution) eg, 300/72 gives you 4.17. By Setting the scale slider to 417%, your output should export at the correct size.
Note: Technically, your image is still at 72 dpi, it's just much larger, so if you want true 300dpi images, you'll need to batch process your exported images using Photoshop to adjust the size and dpi.
Also, I updated my previous post on 'organize', adding a new pic, and some notes on pro mode.