Charis SIL: Bitstream Charter for Windows
One of my, if not the only, favourite Linux built-in font is Bitstream Charter (pictured below). Charter is a classic professional serif typeface which is primarily designed printing. Despite that, It looks very beautiful on screen, especially on large size, as it is on print.
Unfortunately, Bitstream Charter is not easily available for Windows. If you’re trapped on Windows and Georgia  (seriously, you’re not using Times New Roman are you?) does not satisfy your serif needs, there is still Charis SIL (download page). It looks very similar to Bitstream Charter, since Charis SIL is derived from it. From my slight observation, it looks a bit thicker than Charter, but still maintains the professional serif look. It also has a taller line-height giving it a ‘double space’ feel right away.
On a related note, I would like to share a link: The Secret Lives of Fonts. A recommended read, especially for those still studying in collage :)