I'm selling my first ever real silkscreen printed t-shirts, through Coudal Partners' Swapmeat. It's limited to 119 shirts in M, L, and XL, $19 each (paypal). Ever have trouble finding someone at a meetup? This should help. Also, if this goes well, I'll be doing more designs in the future.
No one asked for it, but I figured what the hell: custom MetaFilter baseball t-shirts are now available.
So there's shirts and mugs now. Full disclaimer: I'm making $3 from each shirt sold, to help support the site, while the mugs are being sold at cost.