I've ruined a lot of my favorite tshirts in the workshop, so I'm constantly on the look out for quality replacements. I can usually find decent selection at Old Navy or Target, but they tend to sport goofy graphics that appeal to the 13 year old pre-hipster crowd. Likewise, its easy to find great looking surfing/skateboarding/tool company shirts at Etsy or elsewhere, but always at a hefty price.
Recently, I started ordering tshirts directly from the Powermatic/Jet/Wilton website. The Hanes cotton shirts are $5.95 each and look respectable. They do shrink a bit, despite their "pre-shrunk" labeling. The websites sell other logo wear and promotional gear, but their tshirts are the only bargain. Check 'em out.