I used Nokia's fonts(including Pure Text) and found they are good, not the best ones.

Then I switch to cantarell, which is too wide comparing to other. Next, I dropped Ubuntu Family, then Pt Family, later Droid Family, then Linux Libertine Family.

The latest font I am using now is Ubuntu, yes, 2 days ago, I went back to Ubuntu, with 0.8.0 new release. Pretty and Bold shape. Although mono I would have Liberation Mono everywhere.

I'd suggest firing up a word processor and comparing a similar text with different fonts. Some fonts are wider, some are higher, etc. A very wide font is obviously undesirable on a small display.

Having said that, I'm using the not-very-compact Century Gothic because I like the delicate appearance and good readability:


EDIT:
Here are a few candidates I would consider. All fonts are in the same size. First four are nice, the last one would be VERY compact :D

I like light fonts, if you need only latin characters I can suggest the leage of moveable type for some nice looking fonts, especially raleway.

I also like segoe UI and segoe UI WP from microsoft, as well as nokia pure (very similar)

It's all about Moth-ra ****ing Roadgeek Engschrift.

http://www.fonts2u.com/roadgeek-2005-engschrift.font