Wow! This is like having a complete ELT library at your finger tips and it's all free! PDF Geni is search site that gives you free access to PDF e-books all of which are freely available on the web.
It isn't limited to ELT and can be used to search for any subject. I had a look for a few things which might be useful for EFL / ESL teachers and found loads of free materials.
Check out these searches:
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