My local CSC's branch in Clarksburg, MD (301-353-1150) provides outstanding service and super-fast delivery. Not the cheapest place in town, but they have the resources of many locations. If it's not stocked locally, they can get it fast.

I agree that Clifford of Vermont is probably your best bet for small quantity purchases. Again, not the cheapest, but they will sell you ten feet if that's all you need.

Capitol Cable, in Germantown, MD has amazed me as well with regard to the extent of in-stock inventory. Pricing is better than others but since I don't deal with them as much, I don't get large discount levels.