The movers will be arriving at our apartment in three weeks. The container size allowance we were given has the same dimensions as the one which carried all our stuff over to Ireland 11 months ago. But over the course of a year, we've bought a ton of gifts, travel guides and even some furniture. We don't have room to ship this stuff back to the States, nor do we want to.
If you find yourself in the same situation, I've found that the Ireland Boards web site is pretty good for selling off stuff. There is no fee to post an ad. I posted an ad for two computer desks and had two offers within a week (including pictures is recommended). Boards.ie is partnered with Ireland Adverts; figuring out how to post a free ad wasn't that easy, but once I realized that my free Boards subscription included Adverts, and I needed to go to the Adverts link inside the Boards web site to post an ad, it all worked out.
Charlie Byrne's Bookshop in Galway city centre also purchases used books. I'm going to be taking several of my once-used travel guides there before we leave.
Another great way to shed yourself of books -- in the spiriting of sharing and giving -- is Book Crossing. I have received books from other Book Crossing members in Europe, and I've also sent books to Americans who requested them. Members can even leave books in cafes, airports, bus stations, etc. (called a "Wild Release"), to see what stranger picks up your book, logs onto the web site and records the book's current location. (Members number every book with a BCID code inside.) I've released four books into the "wild" in Dublin, but haven't received any notifications that they have been "caught" yet.