Part of the Practical IDL Programming
Harris Geospatial provides product information about IDL (e.g., current supported platforms), as well as marketing and technical support information.
The Usenet newsgroup comp.lang.idl-pvwave is an active discussion forum for IDL programming issues, and is frequented by many expert IDL programmers who are willing to answer questions. You can also access the newsgroup via Google Groups.
The Astronomy Library includes thousands of IDL procedures and functions developed by the astronomical community. This site also offers a searchable index and a comprehensive list of links to other IDL-related web sites and project specific IDL libraries, including a library for reading and writing data in the Flexible Image Transport System (FITS) format.
The Applied Physics Laboratory Library at Johns Hopkins University is a comprehensive general purpose IDL library containing over 600 procedures and functions.
BBEdit is a point-and-click text editor for MacOS platforms.
The Ghostview and GSView applications for Windows and UNIX may be used to view PostScript files created in IDL, and to create Encapsulated PostScript files with preview images.
Many of the best IDL programmers maintain web sites that provide high quality IDL source code relevant to a range of disciplines.
Michael Galloy provides a fascinating IDL blog and information about his book Modern IDL.
David Fanning maintains a comprehensive IDL website that includes a collection of illustrative and useful IDL programs; a valuable list of IDL programming tips; information about his book IDL Programming Techniques, and many other useful resources.
Craig Markwardt has implemented a robust set of generalized curve-fitting routines in IDL and also provides a useful set of array and graphics utilities.