Some of my alltime favorite blog postsNumber TheoryFractionsBar Modeling (aka Bar diagrams, tape diagrams, etc.)Number SenseExpressions and EquationsMARS: RealLife Equations
MARS: Laws of Arithmetic Sue Mercer's unit on Order of Operations (if you use this please pay at TeachersPayTeachers.com) See more at supermathunits.com Online Encyclopedia of Integer Sequences Ratio and ProportionMary Dooms 6th grade wiki
MARS [ Proportional and Nonproportional Situations Lots of good stuff on Mathalicious and in 3acts Data and StatsProblem Solving ResourcesThree Act Math/Rich TasksMathalicious.com (paywall to get all their lessons, but they have a lot to samples) Lots of good stuff on ratio and proportion
Mr Stadel 3 Act Math Catalog Dan Meyer 3 Act Math Catalog Robert Kaplinsky YouCubed To Help Struggling StudentsGap Closing
Reteaching v. Reengaging Number Sense Games from Butterworth Survivor Algebra on CoolMath.com Special Purpose SitesVisual Patterns
Graphing Stories Estimation 180 Math Mistakes 101 Questions Math Arguments 180 Math Talks by Fawn Nguyen Nix the Tricks by Tina Cardone et al Which One Doesn't Belong? Mary Bourassa 6th Grade Common Core ResourcesAwesome wellorganized collection of Grade 6 Tasks by Geoff Krall (I think)
Howard County Common Core resources Mr Kraft 6th grade math wiki Inside Mathematics  6th grade Content Tasks and Problems of the Month Engage NY  NY State Common Core aligned curriculum materials Ohio Resource Center  not just grade six, lots of common core stuff 7th Grade ResourcesTeacher Resource Page
http://cstonercommoncore.pbworks.com/w/page/60666531/7th%20Grade Mattress scaling lesson from Fawn Mullet Ratios by Mr. Vaudrey Function Carnival and Desmos for Teachers from Desmos and Dan Meyers Barbie Bungee Number Warrior On multiplying with signed numbers Probability Carnival  from divisible by 3 (Andrew Stadel) Scientific notation  ask a different question 8th Grade Resources
Teacher Created Text Book  found link through Mary Dooms
Stats and Probability Resources Great approach to factoring quadratics two posts: Here and here James Tanton has great stuff on quadratics and more. Although still pretty abstract, his videos are everything Khan Academy's aren't. Check out his YouTube channel also. Problem Solving/Enrichment ResourcesNRICH
Math Forum Grace Church Abacus Math Math Munch Exeter problem sets Gday Math from James Tanton Five Triangles Math Sidwell Friends Enrichment for Elementary Students Math Contest Problems
StandardsBased GradingThink Thank Thunk Shawn Cornally's brilliant series on SBG
ActionReaction Frank Noschese (who teaches physics) on SBG How Maths Must Assess from 2006! by Dan Meyer Jason Buell on SGB SBG grade books: Active Grade and Jumpro.pe Miscellaneous Math Teacher ResourcesNational STEM Centre UK
Illinois Council of Mathematics TEachers  Resources Page Kansas Common Core Site (flip books, etc.) Three to 11 (mental math, teacher resources) including curated math games links Center for Innovation in Math Teaching  Book 9 For New TeachersNice collection of blogposts from Mathy
Building Our Classroom Malcolm Swan Must Read for New Math Teachers For Elementary TeachersA collection of fractions games. from Max Ray at the Math Forum
Number Talks Videos from Inside Mathematics Math Frames (lots of games, many for primary age) Other teacher stuff 
Blogroll

Books (with pages made of paper)
Beyond Pizzas and Pies
Teaching with Problems and the Problem of Teacher, Lampert
Number Talks,
Thinking Mathematically,
Teaching with Problems and the Problem of Teacher, Lampert
Number Talks,
Thinking Mathematically,