Is there a file explorer/manager for the command line?

Well there is midnight commander:

To install: sudo apt-get install mc
To run: mc

And also Last File Manager:

To install: sudo apt-get install lfm
To run: lfm

Ranger:

ranger is a file manager with VI key bindings. It provides a minimalistic and nice curses interface with a view on the directory hierarchy. The secondary task of ranger is to psychically guess which program you want to use for opening particular files.

• UTF-8 Support
• Multi-column display
• Preview of the selected file/directory
• Common file operations (create/chmod/copy/delete/...)
• VIM-like console and hotkeys
• Automatically determine file types and run them with correct programs
• Change the directory of your shell after exiting ranger
• Tabs, Bookmarks, Mouse support

Another useful filemanager that can be operated entirely from the keyboard is vifm and it is available in the repositories. You can install it with:

sudo apt-get install vifm

It has an ncurses style interface and is ideal for using on servers. It is quite similar to the other dual pane file managers mentioned except that it supports all the vim shortcuts. If you know all the various ways of operating in vim, then this file manager will be ideal and you will not need to learn another slew of shortcuts.

A vifmrc is created in a ~/.vifm folder when the program is installed, so you can add your own personal configurations and keybindings. However, to fully use all the more recent features such as customising keybindings you will need to compile the latest version from the project site, and make sure you install the minimum build dependencies libmagic-dev and libx11-dev. The version in the repositories is fine and stable, but it is quite an old version (0.4.2) and the current version is 0.7.4.

Just like in vim, you can press Shift+: to enter the command line inside the file browser and perform many actions, as as noted in the documentation at the Sourceforge site. The creator of the program indeed uses it for his home server, as he shows in his screenshots here, so I think the program would be perfect for you, or anyone already familar with vim.

You could take a look at Dired Mode for Emacs. Though it's integrated to Emacs (so you have to learn the whole stuff), it's so much useful and nice to use that it could be nice to try it.

You can display a repository in in the console by running it in no-window mode:

emacs -nw /path/to/your/repository/

Dired is a visual directory editor, a computer program for editing file system directories. Dired runs on any Emacs platform. Its commands are generally more modal than most Emacs commands because Dired is a specialized major mode on its own. Dired can perform all expected operations; in operation and use it is akin to an orthodox file manager like Midnight Commander.