If you're the sort of person who likes to stick notes all over the edges of your monitor, you can save a tree and put the notes right on your screen using Outlook.
The Notes feature is available in both Office 2007 and Office 2010. You can find them tucked inside the New Items, More Items sub-menu but it's so much faster to just press Ctrl-Shift-N to generate a new note and type away:
To find notes quickly if they disappear, you can Alt-Tab between active windows or, if you're using Windows 7, simply mouse over the Outlook icon on your Taskbar to view and select from among the Outlook windows you have open.
To find your notes later after they've been closed, just click the Notes tab on the Outlook Navigation Pane: