Sometimes I have to keep information in mind, that is not a task itself, but on which future tasks might depend on. For example, "Mr. Monkey will not be around during the first half of July!"

Now, although it would be easy to store this information somewhere else, like in Evernote, it is useful to have it in immediate physical, and therefore psychological, proximity to the project/context it belongs to, i.e. in the particular task list. So, I simply create a task containing that info and tag it with #info.

Furthermore, by adding a smart list that shows all your non-tasks tagged with #info, you can have easy access to everything you want to keep in mind while planning your stuff.