In case you haven't, google "Irfanview" and download it. It's a free, windows-based image viewer that is about as lightweight and speedy as they come. It comes with a thumbnail viewer called "Irfanview Thumbnails" that it the fastest thing I've found for viewing RAW files.

I use Irfanview Thumbnails to select the images that I'm going to edit for reception slideshows. Two weddings ago I edited AND processed 59 images in 25 minutes for a slideshow, and last weekend I did the same in 45 minutes. My workflow is:

1) Dump files to hard disk.
2) Open photo location (the folder I dumped to) in Irfanview Thumbnails
3) Drag-n-drop the photos that I want to edit in the slideshow to a different folder
4) Open Lightroom and edit only those photos.
5) Voila - slideshow!

It's worth mentioning that you should download the plugin pack if you want RAW support.

If I remember correctly, I used to use this program when I worked for a metals company. It was the only program that could open all of the random image files that came in from different countries.

From what I remember it was well worth the the free download.

Personally I like XNview better but that certainly is a good program as well.