The Book-Hoarders' Dilemma: How Do You Recycle?

In honor of Earth Day, I'd like to bring up a question that gets a bit sticky among writers. How do you -- or do you -- recycle your books?

I buy a goodly number of books each year, books I've read about or friends have recommended, authors I've learned to love, and from time to time, a book that catches my eye in the store for some reason. Along with these, I receive numerous free promotional books from writers' conferences and other sources. More than I could read, even if I chose (which I don't, since many aren't the type of book I'd enjoy) to only read freebie books in any given year.

As much as I love books and want to support their authors, the necessity of getting rid of some is clear. My space for storing both unread and already-read books is finite, so what's the best and most responsible way to keep my house from looking like one of those stacked-to-the-rafter hoarder homes?

Here's how I handle it:
1. I try to pass along new sample books I know I won't get to to readers I believe would appreciate them. Hopefully, the books will act as a "gateway drug" and hook the readers on a brand-new author.
2. Share books I've read and loved with friends/critique partners/my sister if I believe they'll love the book as well. If I know I won't reread the book (I'm not a big rereader, and I never reread books with a big mystery element, as knowing the solution would spoil the experience for me) I may "loan out" the book with the caveat that it must never be returned.
3. Older books may be donated to the library book sale to help support the purchase of new books. Occasionally, brand new, unread books (samples, again) may be donated to the library to place in circulation. Theoretically, this has the potential of interesting many readers in the authors' work.
4. If I've read a book and didn't love it or even if I liked it but can't think of anyone else I know who would (I read some pretty odd books), I might turn it in for credit at a local new/used bookstore. I have to admit, I'm ambivalent about the places. As a reader, I discovered many authors I grew to love (enough to subsequently buy all their new releases brand new) at UBS's and really appreciated them -- along with public libraries -- when I was too broke to afford new books). I've always found out-of-print backlist books that I've treasured in such stores. As a writer, however, I know there are a good number of UBS devotees who eagerly wait for my books to show up used, which deprives me of income. I hope that someday U.S. authors will receive some sort of royalty on subsequent sales (or even library check-outs), because unless you're one of the big names, you're usually surviving on a narrow margin.
5. Very, very rarely, I (gasp!) throw away a book, either because it's horribly yellowed or mildewy or falling apart (my rescue mutt, Jewel, enjoys devouring a good novel as much as anyone) or because the book was so seriously offensive that I can't imagine passing it on to anyone. (I've come across maybe two books in my life that elicited that reaction. Both of which included completely-gratuitous sexual violence for the purpose of titillation. I'm not a prude and don't mind reading explicit adult content, but there's a line.)

In spite of all these steps, my numerous bookshelves are still double-shelved, I have stacks of unread books around my bedroom, and there are always a few current reads lying around the house. Lately, I've been eying my large collection of autographed copies (most of which are personalized, with my name) and wondering if there's an acceptable way to cull them without resorting to a black Sharpie or Exacto knife. (I shudder at the thought of defacing the books!)

So what do you do with your excess books? And what's the right and "moral" way to handle the onslaught?