Back to school sales are a tabletop gaming hobbyist boon. Keep an eye on local sales for all sorts of gaming and crafting goodies at excellent prices. Some of the best deals I find are at Walmart, Walgreens, Target, and other chains. Some things to watch for include -
Glue - White glue and glue sticks are useful for all manner of tabletop gaming projects. Many places, particularly big box stores, will have white glue and glue sticks on sale for as low as a quarter or a dime in the smaller portions. Watch out for glue sticks that have color in them, though, as the bleed through can botch up an otherwise good looking project.
Paper - From legal pads to lined loose leaf paper, pads and reams or half-reams are available in quantities and pricing that make stocking up at this time a year a must. Also, check the other sections for better pricing on printer paper.
Graph Paper - I mention this separately from other paper because it can sometimes be shelved apart from its cousin and then forgotten while shopping. It can be tempting to get grids at smaller than four squares per inch but be cautioned that while it might seem you can get more drawing on the page, you might also find it tougher to reference during gameplay. Be certain to also look for hex-grid paper while you are at it.
Pens, Pencils, Crayons & Markers - Make sure to grab plenty of writing instruments at this time of year. A couple of packs of pencils and pens are always handy to have around but don't forget that colored pencils and crayons can be very useful in color coding your creations. Plus, keep your wet erase, dry erase and permenent markers separate so you don't wind up ruining a white board, battlemat and other maps that you might have laminated so that you can mark them up temporarily.
Also, grab a pencil sharpener or two and keep an eye out for hole punches, folders, binders, rules, tape measures, pencil cases, scissors, post-it note pads, construction paper, poster board, and some places will even discount their foam board at this time of year. As always, with the hobby stores, make sure to check their web sites for coupons before heading out.