Such a Thing as Free

A friend found his new-to-him school in need of Algebra I and Geometry textbooks - for cheap or free. I took the Twitters, and people responded quickly and generously. Thought I should collect their suggestions.

Free Curricula
My first suggestion was Geoff Krall's (@emergentmath) Problem Based Learning maps. Amazing work. It's a worklife dream to develop a collaborative site like this where we could all link our best lessons and do some informal lesson study.

My second suggestion was Illustrative Mathematics, Algebra and Geometry (plus everything else).

Then #mtbos hit the gas:

• David Coffey (@delta_dc) reminded me of the Georgia Common Core Materials.
  When he wasn't Khan-baiting.
  This is where I would start. Very complete, a lot of excellent lessons and compatible web resources, even including 3 Act structure stuff. 
•  Bridget Dunbar (@BridgetDunbar)  ·  out of Utah: Mathematics Vision Project.  They follow integrated sequence...but good materials.
• Engage NY, Algebra and Geometry (but complete K-12, math and ELA).
  Inconsistent quality to me, but a lot of good stuff and assessments are there, too.
  Lisa Bejarano (@lisabej_manitou) recommended one of these two.
  Dan Anderson (@dandersod) noted it, but does not love it.
•  Macomb ISD Math (@MISDMath)  ·  have you looked at the EMATHS materials?
  That's the online materials for Michigan's virtual schools. New to me.  Looks thorough, with PD materials, lesson plans, activities-based and assessments.
• @geonz  shared Algebra2go. Early, online algebra curriculum with videos and homework.
  

Other Ideas

• Peg Cagle (@pegcagle)  suggested: Visit Abebooks for old Key Curriculum Press materials-brilliant rigorous & coherent-a bargain at full price, now available for a few bucks.
  I noticed some IMP stuff there. Love IMP.
• Justin Lanier (@j_lanier)  ·  There are the Exeter and Park School problem sets, which are freely available.
  At Exeter they have been problem-based for a long time, in 12 student classes. Read more about their Harkness method.
  The Park School curriculum is available on request, but you may have to nag them.
• Raymond Johnson (@MathEdnet)  ·  Not as cheap as they used to be, but College Prepatory Mathematics is worth considering.
  Samples here; those are good stuff.

I also let him know about the single serving sites:

• 101 Questions (#anyqs)
• 3 Acts (spreadsheet)
• Agree or Disagree Math
• Daily Desmos
• Estimation 180
• Graphing Stories
• Math Mistakes
• Visual Patterns
• Would You Rather...

That list lives on my Reading Recommendations page. I also put in a plug for GeoGebra (of course).

If you have experience with any of these things, or know of other resources, please list them in the comments. And thanks to everybody who responded or retweeted.