Like Bill, I've had a problem accumulating books, but I've been much better about this for the last few years. I was using Safari Books Online for a while, but didn't really use it enough to justify the $120/year or whatever it was. It appears the price has gone up to $20/month, which is double what I think I used to pay; definitely can't justify that.
A handy little Greasemonkey script from my new next-door cube-mate, Josh Staiger, Wake County Library Lookup, opened my eyes up to a free resource: my local public library. (Thank you Ben Franklin!) If you don't happen to live in Wake County, North Carolina, perhaps you can find a Greasemonkey for your library, here.
I've been a life-long library user, so it's not like my eyes were just opened up to the possiblity of free books, but most libraries don't have a great selection of tech books, or at least recently available tech books. There are options; you're a tax-payer (probably), so why not ask your library to buy a book you want. For Wake County Public Libraries, head over to the Adult Services section at the library, and ask the librarian about this. They'll give you a card to fill out; ours wants to know, along with the usual stuff, the publisher, publication date, and ISBN. Stuff you can get from Amazon.
In lieu of ordering the book, at Wake County you can make a request for an InterLibrary Loan, where the library will attempt to get the book from a different library system. You can do this from your comfy chair at home, via the web. Our library is great; I request books from their (fairly yucky) web interface, they email me when the book is ready to be picked up. Head over to the library, walk over to 'my' shelf and find the labelled book, and checkout.
I just checked out Pragmatic Project Automation: How to Build, Deploy, and Monitor Java Apps, from my library this afternoon. It happened to be the only book, besides the GTD book, on Bill de hÓra's Ten books for the working programmer, which my library had available. I put in an InterLibrary Loan request for another one.
BTW, I just created an Amazon list for Bill's top ten list, plus some of the other books mentioned in the comments.
Of course, sometimes you need to own the book. But many times, you don't. You just need to read it. Or you might want to preview it, before actually purchasing it. A more extended preview than you can get from a visit to your local bookseller.