My systems are easy and kind of straigh forward and I'm not sure if they will be of any use to you. I use Evernote for all my to-do-lists, grabbing pictures of websites, or texts, writing notes, et.
Remember the milk is another to do list that's very simple to use.
As for something more sophisticated, I don't need it so I wouldn't be able to do any recommendation
Before asking, do a search... if you don't find the answer, then ask The purpose of this forum is to help others in the community, that's why it's called Sitepoint and not Linkpoint. SP Guidelines - No fluff.