A good starting point to using IDL is the guide written by NCAS-CMS - 'Using IDL in Meteorology'.

This 133 page guide has many example plots and tips on using IDL.

New in Version 5 (October 2010)
Expanded examples section.
New section discussing in detail how to use the guide routines.
SF - new function to simplify field selection for contour and vector plots.
Quick contour and vector plots on the command line using the /QP flag
CON, F=SF('gdata.nc', 'temp', p=1000), /QP will produce the same plot as example 1.
LEGEND has become GLEGEND to avoid conflict with the new IDL 8 routine.
Plotting rotated grid and WRF data.
Mac and Windows setup instructions.