With no marketing budget there is little hype for many *nix desktop applications. I've found that most of the utilities I use everyday I've learned about from reading newsgroups. I am sure there are many fine applications that I haven't discovered yet.
One application that I've recently started using and I really like is emeLFM, it is a GTK based lightweight file manager. A couple of things I like about it is that it has a built in command line for executing commands without the need for a terminal, and configurable key bindings, and toolbar. It also has file bookmarks -- that comes in real handy when I have projects sitting in specific files.