I really love Palatino font on paper. It is not very readable for large area of text on screen, but works fine in application menus & such. For screen serif fonts, my preference order is: Georgia, Bitstream Vera Serif, URW Bookman L -- depending on availability & rendering.
I can tolerate sans-serif only in low quantities (unless it is a good monospaced font). This is where I am quite grateful for Opera to allow per host|domain user customisation. I don't care for any sans-serif print font at size 12 or 14, so I would like that to be the same as screen font: Trebuchet MS, Bitstream Vera Sans, DejaVu LGC Sans.
For code, I really like a good monospaced font, whether it is serif, sans-serif, or mixed. Nimbus Mono is horrible, which is not as bad as Courier, but Courier New is preferable given all three. My current favourites are: Bitstream Vera Sans Mono, and DejaVu LGC Sans Mono.