The Panoply data viewer, developed by Robert Schmunk at NASA GISS can read and display (as maps and time series) netCDF, HDF and GRIB data sets. The mapping capabilities of Panoply are pretty good for data exploration, and in addition, Panoply can reveal whether a netCDf dataset, for example, is well formed.

Panoply’s help resources are not substantial (which is fine, because it is extraordinarily easy to use), but there is a short description of Panoply here: