Some of you may find this useful when researching carnivorous plants. It's a PDF search engine. The link below will will search for PDFs related to 'carnivorous plants', but obviously you can search for whatever you want.

http://openpdf.com/ebook/carnivorous-plants-pdf.html

For Firefox users who find the above useful, I have written a search add-on:

https://addons.mozilla.org/en-US/firefox/addon/159021