I don't care if you work for an internet company (*cough* chad *cough*) - every man should own a button-down dress shirt. Michael Kors makes some seriously awesome pieces that fit that bill nicely. All are high on style and quality. They have a nice choice of classically sharp designs, as well as more modern (paisley, denim) prints and fabrics.

They retail for around $100, but you can find them for much less. Check out Overstock.com, Gilt.com, and others.

For more traditional online shopping, try their official site (linked here on the 'Shop for it' button), Nemian Marcus, or visit one of their boutiques. There's a nice little one in SoHo here in NYC.