Similar to CRuby

Enigmail

Enlightened Sound Daemon

Erlang (programming language)

ERP5

Mule (software)

Etherpad

Exa (command-line utility)

Exaile

Expr

EZ Publish

F-Spot

Falkon

Far Manager

Fetchmail

Fastest Fourier Transform in the West

FindBugs

Firebird (database server)

Firestarter (firewall)

Firewalld

Flask (web framework)

FLTK

FMSX

Foliate (software)