For me, I never felt like there'd be a huge amount of content that I'd want to convert for my new PRS-505, so I've not researched too many of the available tools out there such as HTML2LRF.
However, since I discovered
Stephen Fry's excellent new blog, that changed. His posts are so long and entertaining, I knew I wanted to read them away from the PC.
So, just to try it, I copied and pasted the text of his 3 posts so far into a Word doc, and dragged it across to the Reader through the Library application. I have to say it worked VERY well indeed. For a very quick and dirty conversion, without installing any new software, I'm very happy with it.
I read all 3 posts+comments at the park today, in total comfort. Each of them was over 100 pages long at the "L" setting so it was very worthwhile couple of minutes doing the conversion.