Check NOAA's GSHHG (Global Self-consistent, Hierarchical, High-resolution Geography Database).
The database is constantly being updated and maintained (latest update since Im answering this Q: July 1, 2013)
a high-resolution geography data set amalgamated from two data bases
in the public domain: World Vector Shorelines (WVS) and CIA World Data
Bank II (WDBII). The former is our basis for shorelines while the
latter is the basis for lakes, although there are instances where
differences in coastline representations necessitated adding WDBII
islands to GSHHG. The WDBII source also provides all political borders
and rivers. GSHHG data have undergone extensive processing and should
be free of internal inconsistencies such as erratic points and
crossing segments. The shorelines are constructed entirely from
hierarchically arranged closed polygons
The data are available in hdf4/3, ESRI Shapefile and binary formats.