Dolphin: http://enzosworld.gmxhome.de/

Looks to be very nice for people not wanting the feature clutter of Konqueror.

If you want features under KDE file management, then youll need Krusader.

Dolphin is available in the Ubuntu repositories.

Edit: I love it. Just the thing for when I slum in KDE. Which I do do sometimes.

PFT.  Konqueror is just ncely cluttered.  

I like my file manager either stupid simple--for opening porn, as the blood flow impedes thought, or really old skool like some sort of commander type thing. I almost liked Gnome-Commander--but its the slowest file manager Ive ever used.

http://www.nongnu.org/gcmd/