I’ve been using the excellent librarything to keep track of my books. I’ll be building a self-hosted version of it Real Soon Now, but until then, I’m putting what I read in there. I’d gotten a bit of feedback from my vast hordes of readers that they are interested in what I read, so you can see reviews as they happen over there on the sidebar of mah blurg. Why librarything instead of GoodReads or Visual Bookshelf or the like?  Because they will export your library back out for you.

If I decide to change over to a new system, I’ll want an easy way to get MY data back out.   Always consider your exit strategy.