Encyclopedia of Reagents for Organic Synthesis (EROS). 8 vols. (CHEM Ref 547.2 En19 1995)
Updated and available online as e-EROS
Contains a database of around 70,000 reactions and around 4,000 of the most frequently consulted reagents. It is fully searchable by structure and substructure, reagent, reaction type, experimental conditions etc. and allows sophisticated full text searches.
Fieser and Fieser's Reagents for Organic Synthesis. 23 vols. (CHEM Ref 547.301 F464r)
Available online.
Online version collects information from various volumes into one entry. Thousands of entries abstract the most important information on commonly used and new reagents, including preparation, uses, sources of supply, critical comments, references and more. Although it is becoming dated, the handiness of this series makes it one of the "standard" synthetic organic reference.
Handbook of Reagents for Organic Synthesis
These are collections of various reagents from EROS that have been compiled into smaller handbooks of similar types of reagents. Some we have in print and others are available online.
Print Volumes:
Online Volumes (through Knovel):