  The all-sky 408 MHz map of Haslam et al. is one the most important
total-power radio surveys. It has been widely used to study diffuse synchrotron
radiation from our Galaxy and as a template to remove foregrounds in cosmic
microwave background data. However, there are a number of issues associated
with it that must be dealt with, including large-scale striations and
contamination from extragalactic radio sources. We have re-evaluated and
re-processed the rawest data available to produce a new and improved 408 MHz
all-sky map. We first quantify the positional accuracy ($\approx 7$ arcmin) and
effective beam ($56.0\pm1.0$ arcmin) of the four individual surveys from which
it was assembled. Large-scale striations associated with $1/f$ noise in the
scan direction are reduced to a level $\ll 1$ K using a Fourier-based filtering
technique. The most important improvement results from the removal of
extragalactic sources. We have used an iterative combination of two techniques
-- two-dimensional Gaussian fitting and minimum curvature spline surface
inpainting -- to remove the brightest sources ($\gtrsim 2$ Jy), which provides
a significant improvement over previous versions of the map. We quantify the
impact with power spectra and a template fitting analysis of foregrounds to the
WMAP data. The new map is publicly available and is recommended as the template
of choice for large-scale diffuse Galactic synchrotron emission. We also
provide a higher resolution map with small-scale fluctuations added, assuming a
power-law angular power spectrum down to the pixel scale (1.7 arcmin). This
should prove useful in simulations used for studying the feasibility of
detecting HI fluctuations from the Epoch of Reionization.
