I will only talk about fonts that are freely available.
Lexia DaMa is very, very similar to Caecilia.
I have used Corel Draw! and I have made samples of identical text in both fonts. I have made both semi-transparent (with diffenent colors) and I have put one text on another to compare them. The difference is *very* small. What distinguishes *Kindle version* of Caecilia 55 from other fonts is that Kindle version has hand-tweaked bitmaps embedded in font for certain sizes.
Lexia is free, Caecilia is expensive, commercial font.
My long time favourites are Gentium, Gentium Book basic, and Ubuntu font family http://font.ubuntu.com/
Many people here like Fontin.
There are also many decent fonts that are available for various Linux distributions, because fonts distributed with Windows are in fact proprietary and non-redistributable.
Fonts used as base fonts in Linux distributions are: dejavu fonts, linux libertine, droid (paid for by Google for their Android project), and others. Just have a look at Ubuntu Linux repositories.