This last weekend, while discussing H.P Lovecraft I was informed that copyright has lapsed and that his collective works have just entered the public domain. Because I'd rather enjoyed the few Lovecraft stories I'd read, I decided to see if I couldn't find some some of them online. What I found in fact is a site that not only fulfills my Lovecraft needs, but does so while impressing the hell out of me at the same time: manybooks.net.
Manybooks, like Project Gutenberg (indeed a great many of the books at Manybooks come from Gutenberg) is a portal to public domain books. But where it really shines is in its clean, attractive presentation and excellent layout. You can hunt through Gutenberg and dig up good stuff, but by contrast I feel like I can leasurely browse Manybooks and let the good stuff find me. What also sets manybooks apart is that once you find a title you want, you have a staggering 25 text formats to choose from! Everything from straight text, HTML, and PDF to a myriad of eBook/device specific formats is supported. Even free audiobooks are linked to, when available. It's awesome and definitely worth taking a look at.