I have a 35% off code good for 3 uses (expires today @ 11:59pm MDT): YXJ1655K
Here is another good for 30% off plus a $20 eDeals card for orders over $75, also good for 3 uses (expires today @ 11:59pm MDT): RXU0010J
I get coupons like this a few times a week by subscribing to STP's Dealflyer emails - it's one of the few mailing lists worth signing up for. While I'm at it, I guess could also plug their Visa card - UPS Ground shipping is flat rate $2.95 per order for most orders when you pay with the STP Visa, which usually saves me another $5+ per order.
I have no vested interest in STP's sales or success, just a frequent shopper. I've found that no other retailer sells Icebreaker merino wool baselayers, socks, hats, etc. for less - stock/sizes are somewhat limited but I can usually buy my wool baselayers for 55-60% off retail after coupon.