While there is an extension in the Joomla Extension Directory (JED) that lets you keep a "To Do" list in the Joomla backend, the easiest way to do this is is to use the built-in "Custom HTML" module. It's not only easy to create but takes little effort to maintain and certainly beats keeping yellow sticky notes all over your desk. Follow these simple steps to set one up in minutes:
Fairly straightforward, eh?
The "Administrator" submenu is visible AFTER you open the "Module Manager". It's suprising how many people seem to miss this. Administrator modules are actually separate from the Site modules, are rarely created, and since the drop-down menus in the Joomla Administrator do not have the same menu items, it's easy to see how people miss this, though.
Another step that's not much of a brain teaser.
The "Custom HTML" module is just what its name suggests. It serves the same purpose as its frontend counterpart.
For the parameters, make sure you give it a Title, set the module to Enabled: Yes, and publish it to the cpanel module position.
Make the list using your editor or code by hand. The list can be any HTML code you want it to be. It's probably easiest to just make a simple ordered or unordered list (numbers or bullets) but if you want to jazz it up with formatting, go for it!
Bonus Tip: Once you've saved your module, you can go back to the "Edit" screen, copy the URL in your browser, and use it to create a hyperlink in your list. This makes it easily accessible from the Joomla Control Panel. The link should look something like this: http://yoursite.com/administrator/index.php?option=com_modules&client=1&task=edit&cid=61