I have long been a fan of Backpack for collaboration. Quite possibly the easiest way to put pictures and notes on a web for a team of people to look at and interact with. However, I never really got the hang of the to do feature. You can add a list - not necessarily a to do list - on any page and even multiple lists on one page. This is handy but then keeping track of all those todos is difficult. ...and what about priorities and dates?
Welcome to Blackboard - a free (bless your little coding fingers) program that lets you do all the above and add notes and set reminders all in one place across multiple pages - brilliant.