There are so many great resources out there, but one of my favorite sites for lessons and tasks this year is from the Mathematics Assessment Project. I’ve already used their Money Munchers and Boomerang tasks as formative assessments. They’ve provided a window into student thinking as well as artifacts in terms of where students are at with constructing arguments.
Another source for MARS tasks can be found at the Sonoma County Office of Education. The list is organized by grade level and include links to Illustrative Mathematics and Inside Mathematics.
I can’t forget NRICH!
I also love the growing list of blogs in my Netvibes reader. However with time being so precious during the school year, I’ve been zeroing in on the post title and the first sentence displayed in the reader. I know I’m missing out on some great writing and ideas, but it’s the only way I can manage right now.
In my delicious account I found this list of tasks. I’m not sure of the source, but it includes rubrics that you can use as is or modify. I also found Cut the Knot. I haven’t used it but I must have bookmarked it for a reason!
Everybody loves Fawn. She goes without saying. The right rail of her blog links to several heavy hitters.
I’m sure I’ve missed plenty, but those are my first places to go for lessons, task, and activities.
Curiouser and Curiouser 
I love NRich! Didn’t think to name it specifically … but a great resource. Love your lists!
Hey Beth! I’ve been using NRich on occasion but need to make it more of a habit!
I’m pretty sure my ex doesn’t love me, and the girl who slapped me in 2nd grade still hates me. There was that parent who wished I’d move back to China for giving her son an F minus. I didn’t come from China, and the minus was a grade-book default if the percentage fell below 40. Graham Smith hated me in 6th grade because I had two good eyes but couldn’t speak English at the time. He wanted me to go back to China too.
Thanks a lot, Mary, now I’m all depressed thinking about the countless people who hate me.
I didn’t know about the rda site. Thank you for this, Mary. You’re a doll. HUGS!!!
“You’re a doll.” My father used to call me that. I wish he were still alive so that I could hear it from him, but I guess you will have to do. You’re not Irish are you?!
I had never seen the NRICH site before, and now I’m completely hooked. I started the year feeling totally lost about my Math 4 because I’m teaching it through open-ended tasks and now I’m just excited and inspired. So thanks for that!
It has some terrific problems and tasks. Well worth perusing!
NRICH is a fabulous resource. I’m glad you found it helpful!