You may have noticed the thingy on my sidebar that says "Random Books from My Library." That widget is from Library Thing, which is the coolest thing on the intertubes, if your definition of cool happens to be cataloging your book collection online and having other people view them.
I've tried for years to make a project out of compiling a database for my (and my brother's) books but interest has always petered out. Last year I was about to nick some library software from some students' thesis (it was either that or study MS Access, which I'm too lazy to do) when Neil Gaiman posted about LT in his blog. I tried it out and have been a Thingamabrarian since.
Of course, not all of our books are listed. What's on there right now is what's in plain sight at home, as well as those I remember purchasing. There are hundreds more packed in cardboard boxes hidden under beds and in cabinets.
Which leads to a dilemma: do I catalog each and every "Choose Your Own Adventure" or "Hardy Boys" book I own? Should I include ebooks? The Baen Books CD I got from my purchase of "War of Honor" contains the first two books of each of their series, which is about 50 more books I technically own. Or how about those books that were obtained through not-so-legal means? Do I list down all the stuff I xeroxed back in college as well as the ones I've downloaded recently? Stolen or not, they're still part of my library.