Manybooks.net on a regular basis. It is one of my favorite places to go when I want to peruse the classics and other free ebooks. You will find the formatting on these offerings is among the best available on the Internet... Just the good stuff, my friends.
And... it doesn't matter if you have a Kindle, Kindle Fire, iPhone or iPad, you can find just the file type you need.
Kindles like .mobi files. iPhones and iPads do great with epub files. If you have the Amazon Kindle app on your iPhone or iPad, you can use the .mobi files, email them to yourself, open the file on your iPhone or iPad and choose to open with Kindle app. It is a really neat and quick way to get a file to your device.