I've always been a fan of rocking t-shirts and sweaters that represent labels. Artist shirts can be a little too "fan-boy" but labels are a little more subtle and usually have a pretty snazzy logo.
MAGNETIC RECOMMENDS: The Barky Turntable
UK blog Millionhands has come through with a line that represents some of the best new electronic music labels in the game, and even has me rethinking my only rock labels, never the artist stance (I'm not mad at the Soul Clap shirt one bit!).
My favorite is the 1. R&S logo t-shirt pictured above, but the six below are pretty damn nice. You can check out the full line on Millionhands.