From Elizabeth's MOMS Club newsletter:

The first weekend of August, starting at 12:01 am Friday morning, August 3rd, and ending at midnight on Sunday, August 5th, marks New Mexico’s 3rd annual tax holiday. School supplies, computers, clothing and shoes can be had at local retailers tax free.

Personally, I prefer to stock up on school supplies every August at Target. Every week they have different specials. I've bought packs of glue sticks, colored pencil sets, notebooks, tape, etc. for very cheap there (like 10-cents apiece). Usually I try to buy enough to last the entire year.

Here's the official list of taxable and non-taxable items for the tax holiday:
http://www.tax.state.nm.us/pubs/B-200_18.pdf