A neat idea I had was - I track my (sizable) print book collection on Librarything.com - I did an export from that database to a csv file, opened that up - did some column deletes and some tweaks to fit everything and in the end of formatting everything, printed to pdf in Excel.
Then I went to Borders for their closeout sales with a handy full list of my books owned so I didn't get duplicates - I called it my anti-shopping list. I also had my amazon wishlist (tweaked a lot from the source html) and converted to an epub - I can use the touchscreen to make notes or highlight books to remove from the list when I find them at a discount someplace and want to remove them easily. Dunno what anyone else thought of the idea, but it saved me a ton of times from buying duplicate books. So I can definitely see uses for it other than "just ebooks". Using calibre I've also used the feature to grab rss feeds and turn them into epubs to read on the sony reader - I read more rss feeds doing that than I have in ages!
