Ranger is a file manager with an ncurses interface. It is designed to give you a broader overview of the file system by displaying previews and backviews, dividing the screen into several columns. The keybindings are similar to those of other console programs like vim, mutt, or ncmpcpp, so the usage will be intuitive and efficient.
MailChariot's only mission is to get your incoming email (for example from /var/spool/mail), filter it through a spam filter, and put it into a spam or ham mailbox. If you don't agree with the spam filter's decision, you can move it to the notspam or notham mailbox and MailChariot will mark the message as ham or spam respectively. This design is mail client agnostic. It is ideal for use on shared hosts where the provided spam filtering is not effective enough.
skd is a tool for the simple distribution of SSH keys in a growing environment. It allow you to create hosts, group them, and link that group a group of users with keys to easily distribute all affected keys. skd generates a DSA or RSA keypair, which is saved to its database and used as the authentication source for skd itself. This keypair can (and should be) additionally be encrypted using a passphrase. This allows you to simply add a user with their key and press one button to grant (and revoke!) the user's access to all needed hosts.