Eknigu Downloadr Greasemonkey Userscript
Do you know eknigu.com, the friendly site which tries to build an index of cool mathematics and physics related books (and much more)? Interestingly, there are some books which are available for free because the author released them under some copyleft license, and you can get those books there. However, I'm not sure if this applies to all books on eknigu.com. You'll have to look for yourself (and don't be intimidated by the fact that most of the site is in Russian).
For quite some time, eknigu.com didn't work for me any longer. I was annoyed by the 15 seconds of waiting before you could actually get something, so it was time I wrote a little userscript to get rid of the problems:
download the Eknigu Downloadr userscript
If you don't know what a Greasemonkey userscript is, look here and here.
Some technical info:
You could get the same result by downloading the page and manipulating the HTML code (you'll know how to manipulate if you read the JavaScript sources). You have to set the form.action to the right URL and the form's input field "id" to the value "go". At the same time, you have to stop the internal JavaScript from resetting the input field "id" to the value "15". This is essentially what the userscript does, although not by changing anything but by adding an additional layer which contains a second form not influenced by eknigu's JavaScript.
