One of the things I want in a contact management system is a quick way
to find out who I haven't pinged in a while. The following code
filters currently-displayed contacts to show who I might want to get
back in touch with. Call it from a *BBDB* window and specify the date
(could be 2006.01.01 for annual, -7 for the last seven days, etc.).
This works incredibly well with the following hacks:

• Emacs: Keep track of messages sent
• BBDB pinging code

I should write a small book about how to build a contact management
system with Emacs. ;) It's insanely powerful, you know.

(require 'planner)
(require 'bbdb)
(defun sacha/bbdb-show-only-no-contact-since (date)
  "Show only people who haven't been pinged since DATE or at all."
  (interactive (list (planner-read-date)))
  (let ((records bbdb-records)
        new-records
        last-match
        omit
        notes)
    (while records
      ;; Find the latest date mentioned in the entry
      (setq notes (or (bbdb-record-notes (caar records)) ""))
      (setq last-match nil omit nil)
      (while (string-match
              "[0-9][0-9][0-9][0-9]\\.[0-9][0-9]\\.[0-9][0-9]"
              notes
              (or last-match 0))
        (unless (string> date (match-string 0 notes))
          (setq omit t)
          (setq last-match (length notes)))
        (setq last-match (match-end 0)))
      (unless (and last-match omit)
        (add-to-list 'new-records (caar records) t))
      (setq records (cdr records)))
    (bbdb-display-records new-records)))

One of the other things I'd like to smooth over is keeping track of
who owes whom e-mail… <laugh>

I use Gnus to read my mail within the Emacs text editor. One of the
advantages of using a mail client that's infinitely programmable is
that you can add all sorts of little tweaks to it. Gnus can be
integrated with Emacs' Big Brother Database (BBDB), a semi-structured
text database in which I store all sorts of weird notes. This little
hack takes the nick field of the database and automatically inserts a
greeting. If someone signs himself as Mikong, I should call him that
instead of Joseph Michael. Similarly, I sign my messages as Sacha, not
Sandra Jean. This little tidbit makes it easier to remember to call
people by their nicknames.

(defun sacha/gnus-add-nick-to-message ()
  "Inserts \"Hello, NICK!\" in messages based on the recipient's nick field."
  (interactive)
  (save-excursion
    (let ((bbdb-get-addresses-headers (list (assoc 'recipients bbdb-get-addresses-headers)))
          nicks)
      (setq nicks
            (delq nil
                  (mapcar (lambda (rec) (bbdb-record-getprop rec 'nick))
                          (bbdb-update-records
                           (bbdb-get-addresses nil gnus-ignored-from-addresses 'gnus-fetch-field)
                           nil
                           nil))))
      (goto-char (point-min))
      (when (and nicks
                 (re-search-forward "--text follows this line--" nil t))
        (forward-line 1)
        (insert "Hello, "
                (mapconcat 'identity nicks ", ")
                "!\n\n")))))

(defadvice gnus-post-news (after sacha activate)
  (sacha/gnus-add-nick-to-message))