Originally posted by rawr Open Lightoom, then open the PEF from within Lightroom. Or open the PEF in Pentax Digital Camera Utility.
Then export whatever you want to publish to flickr as a JPEG, then post the JPEG to flickr. That's how RAW works. You need to process those RAW files into something.
No-one posts RAW PEF's to flickr.
This, btw, is a good reason to also shoot RAW+JPEG. The RAW files will be there for any tweaking and post-processing you might like to do, the JPG's will be there for quick and easy handling of the images.
+1
In addition, you may want to check out Microsoft's Camera Codec pack, so that you can view & preview raw images in Windows Explorer without opening up RAW software.
Download Details - Microsoft Download Center - Microsoft Camera Codec Pack (This codec is only available to Windows 7 or Vista.)
Lightroom 3 has Flickr export built in. See this video: