There’s something new in Gmail! (again).
Check out the Labs area in your Gmail. There is a new option in there. Tasks.
Now, when you select an email in your inbox etc. you can add it to a task (in the more actions) menu.
When you add a conversation to a task you get a little popup listing your tasks you can add a due date, comment etc.
If you have keyboard shortcuts enabled you can just use <shift> + t
Do you think tasks in your Gmail will make you more productive?