You can use planner-multi.el to associate a task with more than one project. That way, you can easily keep GTD-style context lists as well as project-related lists.
To use multiple projects, add the following to your ‘~/.emacs’:
(require 'planner-multi)
Under GNU Emacs, you can specify multiple projects by separating them with a single space. For example, you can specify planner doc when creating a task to associate the task with those two projects.
Under XEmacs, you can specify multiple projects by typing RET after each entry and terminating the list with another RET. For example, to specify planner and doc, you would type planner RET doc RET RET at the prompt.
If you want to see an overview of all of your tasks as well as
project- or context-specific lists, you can set
planner-multi-copy-tasks-to-page to your overview page(s). For
example, set it to ‘TaskPool’ to be able to see an overview of
all of your unfinished tasks. You can also set this to multiple pages
such as ‘[[TasksByProject][p]] [[TasksByContext][c]]’ and use
planner-trunk.el to sort and organize tasks for easy reference.
(see Grouping Tasks)
Automatically copy newly-created tasks to the specified page.
By default, tasks are removed from
planner-multi-copy-tasks-to-page when you call
planner-task-done or planner-task-cancelled. If you
prefer to keep a copy of the task, remove
planner-multi-remove-task-from-pool from
planner-mark-task-hook.
If you want to use a different separator instead of spaces, customize
the planner-multi-separator variable.