ToDo is often used in a PersonalInformationManager for things which have not been completed. This is a more universal version than that of comments made in source code. It is often scratched down on the back of envelopes, napkins from lunch, a 3 by 5 card, or in a formal notebook dedicated to Time and Information management. 
----
Enjoys a small amount of use to tag ToDo items on some wiki pages; click on the title of the page and maybe you can help the author out.

----
TODO is often found in code indicating that something isn't completed yet. This has become so common that there's now an official @todo JavaDoc tag. Most pages on the wiki citing ToDo are using the term in this way. 

 /**
 * @todo : take over world
 */

Pros and cons discussed on the more general FixmeComment page (critique by M.A. moved there).

FixmeComment CommentCostsAndBenefits
CategoryLanguageFeature
-----

WikiAsPim IsAnythingBetterThanPaper ToDoList

----
CategoryWikiTag