My Cross-Check commuter/brevet/gravel-grinder:
X-Check frame/fork
Velo-Orange headset/stainless fenders/front randonneur rack
Thomson seatpost/Profile Aris stem/Salsa M/A Bell Lap bars
Tektro R200 levers/Tektro CR720 brakes
Sun CR18 rims (32h) DT Spokes, SON28 front hub, IRO high flange rear (fix/fix)
SRAM S300 single crank with GXP BB/Shimano MX freewheel/SRAM PC-1 chain
Nashbar house brand SPD pedals
Bagman support rack/Carradice Pendle/Berthoud GB28 front bag
Kool-Stop pads/Panaracer Urban Max 32mm tires/Cinelli glow-in-the-dark bar tape
I purchase my stuff from a variety of sources locally and online, but my favourites (online) are:
Bikeman and
Nashbar