The Census Bureau’s TIGER/Line is the authoritative repository of US streets and features data, regularly updated by municipalities and counties. For-profit mapping services augment the data and use drivers to make sure they’re on top of streets changes, but you can do a great deal of work with just Census and municipal GIS data.

TIGER's great, but if you're going to use it you might as well just use OpenStreetMap in the end; a lot of the data in the US is based on TIGER data and then reviewed, as TIGER has had a lot of issues with things like misnamed roads and misalignments of roads.

Used Tiger as my first online map in the mid 90s, thanks for the blast from the past. Probably found it thru "Cool site of the day."

The United States Geological Survey releases tons of mapping data.