We've been getting quite a few similar requests from our Microsoft Dynamics CRM clients, many of whom have expressed at an interest in improving the entry of NAICS and SIC codes for business users.
The solution we developed with was to generate custom entities that use picklists to simplify finding the correct codes. It works well - each custom entity contains all the current codes and is easily updatable when new codes are released. The entities write the codes or industry descriptions back to the parent entity (e.g. leads and accounts) for use in reporting and are of great help in developing targeted marketing lists. Each entity uses dependent picklists to narrow the code selection from macro sector to the full category code, making even the most specific ID easy to find. The picker is activated by the user double-clicking the code or code description. You can see the NACIS code lookup entity in action below. If you’d like to install this for your CRM organization, you can purchase the HK-NCP 2009 add-on directly from our web store (contact HubKey if you'd like more information). Alternatively, you could give it a bash yourself - comments section open below for anyone who gets stuck!