I'm glad to join all the other bibliophiles here.
In Brisbane, Australia, we have an organisation called Lifeline (they provide telephone counselling to depressed, suicidal people) and twice a year they have a huge sale of donated books. The prices are really cheap and I suppose it brings out the hunter/collector in me as I search through the hundreds of thousands of books for a bargain.
The other good point is that you know that all the money you spend is going to a good cause. I always come out with at least one box full of books.
Luckily there don't seem to be too many other people interested in natural history so I am able to get some real bargains - mammals of North America, flowers of
Singapore, Hinton on Australian shells and Bell-Cross on
Rhodesian fish (I used to work with him as a student!!).
Cheers
Pete