Org-bibtex is responsible for handling bibtex citation in orgmode. In contrib library there is an addition (org-bibtex-extras.el) by Eric Schulte. This can be used as an easy way to manage an annotated bibliography in orgmode. You can find a video demo to make the setup here.

In your init file you should add the following chunk.

;; load contrib library
(add-to-list 'load-path
             (expand-file-name "/path/to/org-mode/contrib/lisp"
                              (file-name-directory
                               org-find-library-dir "org")))

;; manage citations
(require 'org-bibtex)

;; export citations
(require 'ox-bibtex)
(setq org-bibtex-file "papers.org")

There are three basic commands:

• M-x org-bibtex to export the citations in a bibtex file
• M-x org-bibtex-yank to import a citation from bibtex text (clipboard)
• M-x org-bibtex-check-all to check the validity of the entries

Note that below each heading you can keep your annotations.

* The Org Mode 7 Reference Manual-Organize your life with GNU Emacs
  :PROPERTIES:
  :TITLE:    The Org Mode 7 Reference Manual-Organize your life with GNU Emacs                  :manual:
  :BTYPE:    book
  :CUSTOM_ID: dominik2010org
  :AUTHOR:   Dominik, Carsten
  :YEAR:     2010
  :PUBLISHER: Network Theory Ltd.
  :END:
This line is my annotation for the entry of Org Mode 7 Reference Manual.
* A multi-language computing environment for literate programming and reproducible research    :babel:
  :PROPERTIES:
  :BTYPE: article
  :AUTHOR: Eric Schulte and Dan Davidson and Tom Dye and Carsten Dominik
  :JOURNAL: Journal of Statistical Software
  :VOLUME: 46
  :NUMBER: 3
  :YEAR:     2012
  :MONTH: January
  :CUSTOM_ID: schulte2012babel
  :END:
Some annotation about babel.

NOTE

In the beginning of the video by Eric Schulte you can see that he evaluates the buffer of org-bibtex.el. If you do not do that you will not be able to yank citations. My routine is that I export and open my bibtex document in a new buffer before yanking a new entry.