apm list コマンドを使用します。
apm list --installed --bare
出力例
Sublime-Style-Column-Selection@1.3.0
atom-jade@0.3.0
autoclose-html@0.19.0
autocomplete-elixir@1.4.2
color-picker@2.0.13
docblockr@0.7.3
highlight-selected@0.11.1
jumpy@2.0.10
language-elixir@0.5.2
language-kotlin@0.4.0
maximize-panes@0.2.0
merge-conflicts@1.3.7
meteor-api@2.20.0
meteor-snippets@0.5.0
pigments@0.19.1
project-manager@2.6.5
source-preview-jade@0.1.1
tabs-to-spaces@1.0.1
trailing-spaces@0.3.2