Here is a list of all namespaces with brief descriptions:

access
admin
administration
assignment
auth
auth_cas
auth_db
auth_email
auth_fc
auth_imap
auth_ldap
auth_manual
auth_mnet
auth_nntp
auth_nologin
auth_none
auth_pam
auth_pop3
Auth_RADIUS
auth_radius
auth_shibboleth
auth_webservice
axmls
backup
block
block_activity_modules
block_admin_bookmarks
block_blog_menu
block_blog_recent
block_blog_tags
block_calendar_month
block_calendar_upcoming
block_comments
block_community
block_course_list
block_course_summary
block_glossary_random
block_html
block_login
block_mentees
block_messages
block_mnet_hosts
block_news_items
block_online_users
block_participants
block_private_files
block_recent_activity
block_rss_client
block_search_forums
block_section_links
block_selfcompletion
block_site_main_menu
block_social_activities
block_tag_flickr
block_tag_youtube
block_tags
blocks
calendar
cc_library
chat
Choice
choice
com
com::tecnick
com\tecnick\tcpdf	PHP class for generating PDF documents without requiring external extensions
comment
completion
condition
core
core_user
countries
course
Crypt_CHAP
currencies
data
datafield
datapreset
datapreset_imagegallery
dbtransfer
debug
editor
enrol
enrol_authorize
enrol_database
enrol_meta
error
feedback
file
filter
filter_activitynames
filter_algebra
filter_censor
filter_emailprotect
filter_mediaplugin
filter_multilang
filter_tidy
filters
FirePHP
form
format
format_scorm
format_social
format_topics
format_weeks
formlib
formslib
forum
glossary
gradebook
gradeexport
gradeexport_ods
gradeexport_txt
gradeexport_xls
gradeexport_xml
gradeimport
gradeimport_csv
gradeimport_xml
gradereport
gradereport_grader
gradereport_outcomes
gradereport_overview
gradereport_user
grades
gradingform
gradingform_rubric
group
groups
HTML_Common
HTML_QuickForm
HTML_QuickForm_DHTMLRulesTableless
HTML_QuickForm_Renderer_Tableless
HTTP_WebDAV_Server
hub
imscc
install
installer
iso6392
JSMin
langconfig
license
lti
mathslib
MCFileManager
MCFileManager\filesystems
MCManager
MCManager\includes
MCManager\utils
message
message_email
message_jabber
message_popup
mimetypes
Minify
mnet
mnetservice
mod	Local Library of functions for module scorm
mod_chat
mod_data
moodle
moodle::mod
moodle\mod\lti
moodlecore
moodleforms
Net_GeoIP
notes
OLE
ouwiki
page
pagetype
PEAR
PHP
PHPMailer
pix
plugintype
portfolio
portfolio_boxnet
portfolio_download
portfolio_flickr
portfolio_googledocs
portfolio_mahara
portfolio_picasa
profilefield
profilefield_checkbox
profilefield_menu
profilefield_text
profilefield_textarea
qbehaviour
qformat
qtype
qtype_calculated
qtype_numerical
qtype_shortanswer
question
quiz
quizaccess
rating
report
repository
repository_alfresco
repository_boxnet
repository_coursefiles
repository_dropbox
repository_filesystem
repository_flickr
repository_flickr_public
repository_googledocs
repository_local
repository_merlot
repository_picasa
repository_s3
repository_upload
repository_url
repository_user
repository_webdav
repository_wikimedia
repository_youtube
role
rss
rss_client
scorm
scormreport
search
Services_JSON
SimplePie
SimpleTest
SimpleTestEx
Solar
SpikePHPCoverage_Parser
SpikePHPCoverage_Remote
SpikePHPCoverage_Reporter
SpikePHPCoverage_Util
Spreadsheet_Excel_Writer
Spreadsheet_WriteExcel
survey
table
tag
theme
theme_afterburner
theme_anomaly
theme_base
theme_boxxie
theme_formal_white
theme_splash
theme_standard
theme_standardold
timezones
tinymceplugin
tool
TYPO3
user
userkey
version
web
webservice
webservice_amf
webservice_rest
webservice_soap
webservice_xmlrpc
webservices
wiki
workshopallocation
workshopeval
workshopform
XML_Parser
xmldb
XMPPHP
Zend
Zend_Amf
Zend_Auth
Zend_Controller
Zend_Date
Zend_Gdata
Zend_Http
Zend_Loader
Zend_Mime
Zend_Registry
Zend_Rest
Zend_Server
Zend_Service
Zend_Service_Amazon
Zend_Service_WindowsAzure
Zend_Service_WindowsAzure_Storage
Zend_Soap
Zend_Uri
Zend_Validate
Zend_Version
Zend_XmlRpc