Basic
compiler 4.8.2	A byte code compiler for Erlang which produces highly compact code
erts 5.9.3.1	Functionality necessary to run the Erlang System itself
kernel 2.15.3	Functionality necessary to run the Erlang System itself
sasl 2.2.1	The System Architecture Support Libraries is a set of tools for release upgrades and alarm handling etc.
stdlib 1.18.3	The Erlang standard libraries
Database
mnesia 4.7.1	A heavy duty real-time distributed database
odbc 2.10.13	An interface to relational SQL-databases built on ODBC (Open Database Connectivity).
Operation & Maintenance
os_mon 2.2.10	A monitor which allows inspection of the underlying operating system
otp_mibs 1.0.7	SNMP management information base for Erlang/OTP nodes.
snmp 4.22.1	Simple Network Management Protocol (SNMP) support including a MIB compiler and tools for creating SNMP agents
Interface and Communication
asn1 1.8	Provides support for Abstract Syntax Notation One
crypto 2.2	Cryptographical support
diameter 1.3	Diameter
eldap 1.0	eldap - Erlang LDAP library
erl_interface 3.7.9	Low level interface to C
gs 1.5.15.1	A Graphics System used to write platform independent user interfaces
inets 5.9.2	A set of services such as a Web server and a ftp client etc.
jinterface 1.5.6	Low level interface to Java
megaco 3.16.0.2	Megaco/H.248 is a protocol for control of elements in a physically decomposed multimedia gateway, enabling separation of call control from media conversion.
public_key 0.17	API to public key infrastructure.
ssh 2.1.2	Secure Shell application with sftp and ssh support
ssl 5.1.2	ssl- Secure Socket Layer.
wx 0.99.2	A Graphics System used to write platform independent user interfaces
xmerl 1.3.2	Provides support for XML 1.0
Tools
appmon 2.1.14.1	A utility used to supervise Applications executing on several Erlang nodes
debugger 3.2.8	A debugger for debugging and testing of Erlang programs
dialyzer 2.5.3	The DIALYZER, a DIscrepany AnaLYZer for ERlang programs.
et 1.4.4.2	Event Tracer (ET), uses the built-in trace mechanism in Erlang and provides tools for collection and graphical viewing of trace data.
inviso 0.6.3	A trace tool for both development and delivered systems.
observer 1.2	Observer, tools for tracing and investigation of distributed systems
parsetools 2.0.7	A set of parsing and lexical analysis tools
percept 0.8.7	A concurrency profiler tool.
pman 2.7.1.2	A graphical process manager used to inspect Erlang processes.
reltool 0.6.1	Reltool is a release management tool. It analyses a given Erlang/OTP installation and determines various dependencies between applications. The graphical frontend depicts the dependencies and enables interactive customization of a target system. The backend provides a batch interface for generation of customized target systems.
runtime_tools 1.8.9	Runtime tools, tools to include in a production system
syntax_tools 1.6.9	A utility used to handle abstract Erlang syntax trees, reading source files differently, pretty-printing syntax trees.
toolbar 1.4.2.2	A tool bar simplifying access to the Erlang tools
tools 2.6.8	A set of programming tools including a coverage analyzer etc
tv 2.1.4.9	An ETS and MNESIA graphical table visualizer
webtool 0.8.9.1	A tool that simplifying the use of web based Erlang tools
Test
common_test 1.6.3	A portable framework for automatic testing
eunit 2.2.3	Support for unit testing.
test_server 3.5.3	The OTP Test Server
Documentation
edoc 0.7.10	A utility used to generate documentation out of tags in source files.
erl_docgen 0.3.3	A utility used to produce the OTP documentation.
Object Request Broker & IDL
cosEvent 2.1.12	Orber OMG Event Service
cosEventDomain 1.1.12	Orber OMG Event Domain Service
cosFileTransfer 1.1.13	Orber OMG File Transfer Service
cosNotification 1.1.18	Orber OMG Notification Service
cosProperty 1.1.15	Orber OMG Property Service
cosTime 1.1.12	Orber OMG Timer and TimerEvent Services
cosTransactions 1.2.12	Orber OMG Transaction Service
ic 4.2.31	IDL compiler
orber 3.6.24	A CORBA Object Request Broker
Miscellaneous
hipe 3.9.3	High Performance Erlang