XFE is another lightweight option: http://roland65.free.fr/xfe/
Since you asked...
As minimalist options, I like:
ROX for its ability to manage an entire desktop simply, but dislike the single-click to open (too long in Windows - hence double-click comes naturally now).
Thunar for its: plugins (e.g. volman etc - allows a complete fully-featured manager if necessary); the "open terminal here" right-click menu; the "you are root warning" when browsing as root.
PCManFM for its tabs (and similarity to Thunar).
Unfortunately, they all fall down when it comes to network browsing. For this single reason, I stick with Gnome / nautilus.
PS: ROX was not replaced by Thunar. xftree was the original xfce browser - not sure what happened to it. ROX is alive and well.
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