Is there a way to obtain a list (possibly with descriptions) of all the casks installable with Homebrew Cask?
The new way to list all installable cask packages is:
brew search --casks '*'
The '*' (or equivalently \*) is necessary and is interpreted as a glob that matches all strings. The quotes (or backslash) are necessary to have a literal asterisk passed to brew search; without them, the shell would glob-expand the * into all files in the current directory.
The general usage is brew search, -S [options] text|/regex/ [...].
The man page for brew has the following information:
search --casks
Display all locally available casks (including tapped ones). No online search is performed.