IWLTBAP has built an online LUTs previewer.
Check out the Demonstration of LUTs previewer by IWLTBAP then give it a whirl yourself.
To test easily all the LUTs of my pack (more that 100 unique LUTs) I built this online previewer.
It's a small tool made to apply a LUT in low resolution on JPG/PNG image.
You have just to drag-and-drop and image in the main area and click a LUT reference on left bar.
The image is preloaded but no uploaded (so response time is extremely fast, even for heavy files > 2 MB).
Once the previewer is fully loaded, you can use it without internet connection, like a standalone application (Mac/PC).
It works on all modern browser, but I recommend latest Google Chrome version for better performances.
Important, each LUT is applied at low resolution on your image to increase speed so don't worry if you see pixelation and banding, it will not appear with the real LUT files (.cube and .3dl).
Image by Paul Nordin.
Music : Squire Tuck – Midnight Chillin' (Extended Remix)