I have just spent time looking through the Rich Maths Task resources on the East Midlands Maths Network, and have found some great tasks to incorporate. They are organized by strand, and some of the tasks are taken from the nRich site, which I have also spent many hours perusing.
Thanks to @ColleenYoung for this sharing this resource with me. This site is listed on her blog under Diigo Rich Tasks List, and the site is labelled Rich Maths Task. There are many other sites to visit on her list, and if they are all as helpful as this one, then I know I will spend many hours exploring.