Since I haven't seen it mentioned anywhere in the Iliad Forums although it 's been around for quite some time there is the Munseys (former Blackmask) website with literally thousands of free books to download (DRM/copyright free).
All books are available in quite a few formats: Mobipocket, HTML, PDF (A4), MS-Reader, S0ny Reader and others.
The address is
http://www.munseys.com/
I hope you all enjoy it