Good software to 'to do' list management

Can any of you recommend good software for ‘to do’ list management? Not project management software, such as Micrsosoft Project. I’m looking for something that will keep track of items, with sub-categories. There used to be a product from Borland (?) called Agenda that was great, but the product was killed.
The main drawback on the ‘to do’ list software on my Palm software is the lack of sub-categories. Thanks.

If you already have a Palm, you could use an outliner to manage the Palm ToDo items. I use Shadow Plan. It can link to ToDo items, or you can just use it instead of the ToDo function. I’ve also heard good things about Bonsai.

scr4 Thank you! Shadow Plan was exactly what I was looking for. Since I read your response I’ve tested it it, created a test file, purchased it, and created a huge new to-do list.