[Android] Aldiko
Aldiko is an amazing freeware ebook reader for the Android. Not only can it read your own ePub format books, but it can also download free books from feedbooks, and paid books from o’Reilly.
Reading books on my Droid is great. While the screen is not as sharp as an e-ink screen, it’s still much better than most mobile screens for reading. Changing pages is accomplished by flicking the screen, or using the volume buttons. There is an inverted mode for night reading. Additionally, you can change the font and font size options to your preference.
For converting your currently owned ebooks to ePub, I’d recommend using Calibre.