A Plug-In from Agile Business Solutions to implement filtered or dependent Lookup fields on forms that do not impede search capability, or involve hacking CRM files
Carlton Colter's set of custom Workflow Activities that offer a bevy of various utilities for string manipulation, math calculation, date math, and advanced RegEx transformation
Microsoft's in-depth analysis of the mechanisms in CRM that can be extended or considered in order to provide security at the attribute-level of entities or records in CRM
Microsoft's KB article on enabling the trace logs for CRM (tracing impacts performance significantly, so do this only when necessary, and disable it when not needed)
Patrick Verbeeten's global CRM event cataloger will help you analyze data passed into and returned by SOAP method calls in a traceable fashion; excellent for debugging
Tanguy Touzard's utility to easily manage all JavaScript customizations, offering export and import capability, and a central management interface for all entities
Orbit One's utility to apply updates to CRM records in bulk within the application, or export to Excel (or another app) and import updates made therein
Tanguy Touzard's utility to configure Bulk Delete jobs based on the results of Advanced Find views; can be used to schedule recurring jobs to clean CRM databases
An article from extremecrm.net on how to use System Center Operations Manager 2007 to monitor a CRM deployment's performance and gathering helpful information on areas to improve
The Microsoft Dynamics CRM 4.0 Performance Toolkit was created by the Microsoft CRM product team to formalize performance testing of Microsoft CRM 4.0. The performance toolkit can be used by the Microsoft CRM partners and customers to collect data to support their CRM deployment decisions.
Compare customization XML files from different CRM deployments to identify the differences, or export records for a custom entity that represents a "configuration", and import them into a different deployment that implements the same entities.
Scott Sewell's utility forks Merijn van Mourik's CRM 3 utility of the same name, and compiles CRM entity and attribute metadata into an Excel spreadsheet for reference purposes