For more granular updates check:

http://www.observium.org/websvn/listing.php?repname=observer

SVN

* Smokeping integration
* Fixed Cisco VLAN tracking
* Much improved devices/ports browsing
* Some improvements to map

0.10.5.2248 ( 5th May 2011 )

* Improve poller/discovery
* Improve option bar option highlighting
* Add support for OSPF discovery
* Add support for CEF switching statistics from CISCO-CEF-MIB
* Add support for UDP6 transport (and others) for SNMP.
* Improved Microsoft Windows detection.
* Juniper ScreenOS CPU/Memory.
* Click to zoom for graphs.
* Force10 support (hardware, os, version, temp).
* Mikrotik RouterOS fixes.
* Fixes to port type and customer detection.
* Improved base URL detection. (*REMOVE* $config['base_url'] from your config.php).
* Add graphing of VPN statistics on Cisco IOS/ASA.
* Migrate entire graphing system to new graphing structure with per-graphtype authentication.
* Add more UNIX statistics graphing from UCD-MIB.
* Add support for XUPS-MIB for Eaton devices
* Add support for JunOS BGP prefix counters
* Add support for Ingrasys iPoMan 1200 series PDUs
* Add support for Socomec Net Vision UPS systems
* Add support for ServerTech Sentry3 power systems
* Add support for VMWare ESX hosts, and listing their virtual machines
* Add support for listing libvirt virtual machines
* MySQL and nginx application pollers
* Add support for IPMI polling on servers
* Add a new discovery parameter to only discover new devices, this can be run every 5 minutes
  to speed up discovery of added devices through the webinterface
* Make a distinction between 'ignore' and 'disable' for ports, like for devices
* Allow overriding sysLocation and sysContact

Release 0.10.7.1 ( 19th July 2010 )

* Minor bugfix release

Release 0.10.7 ( 18th July 2010 )

* Project name has changed to Observium
* rrdcached support
* Support of ADSL-LINE-MIB and new ports display mode designed
  for service providers with DSLAMs and MSANs
* Discovery of new device/os types :
  Apple Airport, Axis Camera, Motorola Netopia, APC Switched PDU,
  Extreme Extremeware, Redback, ZyXEL ZyWALL, DELL DRAC,
  Dell PowerVault, Allied Telesis, Cisco NX-OS, MGE Evolution UPS
  HP JetDirect printers, APC STS/ATS, Mikrotic RouterOS,
  AKCP SensorProbe3
* New structure for device graphing to aid 3rd party addons
* Temperature detection from CISCO-ENTITY-SENSOR-MIB
* Graphing of statistics from DISKIO-MIB
* Ongoing unification of all sensors into one 'sensors' framework
* Detection and polling of frequency, voltage and amperage stats
  for many UPSes and power switching hardware
* Detection of Extremeware / XOS versions and hardware
* Detection of several Allied Telesis devices and their versions
  and hardware
* Added a lot of MIBs

Release 0.10.6 ( 21st June 2010 )

* Changed netstats (icmp, udp, tcp, snmp, ip) stats collection
* Implemented new application monitoring system
* Implemented new includes-based graphing system
* Improvements to eventlogging code
* Replaced interfaces polling code (2x speed improvement on average!)

* Removed, cleaned up or replaced a lot of old and unused code.

* Added support for IPv6 BGP sessions on JunOS
* Added support for Dell Powerconnect and HP Procurve switches
* Added support for Supermicro SuperoDoctor temperature support
* Added support for LLDP discovery
* Added support for Q-BRIDGE-MIB VLANs (basically for non-cisco HW)
* Added support for LMSensors and Supermicro Temp/Fan/Voltages
* Replaced old image-based percentage bar with new CSS bar
* Added Foundry/Brocade support
* Added Juniper JunOSe support

* And more...

Release 0.6.0 ( 28th August 2009 )

* Changed IPv6 database structure and discovery *** DATABASE CHANGE ***
* Added CollectD integration code
* Added fixed mib loading to SNMP commands
* Replaced IPv4 and IPv6 discovery code
* Added support for CISCO-PROCESS-MIB for per-CPU graphing
* Added support for CISCO-ENHANCED-MEMORY-POOL-MIB for per-pool graphing

Release 0.5.1 ( 25 March 2009 )

* Primarily bugfixes to 0.5.0
* Removed GPL'd code and added downloader helper scripts instead
* Added Pseudowire menu entry and configuration option
* Fixed device adding scripts and added port option to web interface
* Fixed interface packets/bits/errors links
* Fixed some non-absolute links
* Fixed device deletion script

Release 0.5.0 ( 24 March 2009 )

* Cleaned up a lot of hardcoded paths
* Cleaned up BGP session polling
* Added CDP-based device link map
* Added sysName tracking for more accurate CDP linking
* Added more search features for syslog, device list and inventory
* Replaced old syslog system with new version, without pipes
* Added more Pseudowire/X-Connect tracking information
* Fixed a lot of URLs to be absolute URLs built from base_url
* Fixed some mod_rewrite rules
* Added basic MAC accounting polling
* Added config display and syntax colouring for RANCID-collected IOS configs

Release 0.4.1 ( 20th Nov 2008 )

* Cleaned up some configuration settings
* Added more connection type rewrites
* Added ability to change device names
* Cleaned up IPv6 and CDP discovery
* Security fixes

Release 0.4.0 ( 11th Nov 2008 )

* Much prettier front page
* Tidied up service checking layout
* Added MPLS VRF tracking
* Added Pseudowire/X-Connect tracking
* Basic front page customisation
* Fixed aggregate graphs
* IPv6 address tracking
* View for ports with errors
* Added some JunOS support

Release 0.3.2.1 ( 27th March 2008 )

* Minor bugfix to interface discovery engine.

Release 0.3.2 ( 26th March 2008 )

* Added BGP peer detection and watching
* Cleaned up the front page and made it more useful
* Added better syslog support
* Added some Juniper Netscreen support
* Wrote a better OS detection system
* Added some billing features
* Rewrote and restructured a lot of the discovery
* Rewrote some polling stuff

... This release is greatly improved, and threatens
 to actually work properly for people other than me!

Release 0.3.1 ( 30th November 2007 )

* Fixed a great many things and made it prettier!

 This release took so long that I've largely forgotten
 what's been changed. Again!

Release 0.3.0-pre1 ( 24th June 2007 )

* Added VLAN features for cisco devices
* Added scripts to check for interface errors
* Added extraction of current interface rates from rrd files
* Added some syslog stuff
* Added email notification for device reboots

.. Lots of other updates, most of which i've forgotten about!

Release 0.2.5

* Added new CDP detection code and proper CDP link removal
* Added service addition page
* Added device overview
* Added more interface pages
* Added syslogging using syslog-ng
* Added temperature monitoring and discovery
* Added TCP/IP/UDP/ICMP statistics collection and graphing
* Fixed some graphs
* Tidied up some font sizes
* Added stylesheet variable into config.php to allow custom files to be used

Release 0.2.4

* Fixed some misnamed files
* Fixed some hardcoded binary locations
* Removed some messy AJAX
* Replaced the menu bar
* Added some new menu items
* Cleaned up presentation of some pages

Release 0.2.3

* Fixed some broken graphing code
* Added host add/remove to web interface
* Added host/interface/service status to web interface
* Tidied up some code

Release 0.2.2

* Replaced old layout with new 'Project Observer' layout
* Added recognition of SNOM SIP phones, data collection and some graphing
* Modified standard layout to remove Vostron-specific elements
* Added cpu graphing for ProCurve devices
* Added tabs for device page and AJAX loading of contents
* Detection of HP ProCurve devices
* Detection of m0n0wall devices by new snmp-id
* Can now disable the Transit, Peering and Customer sections
* Added some tabbing to Interface
* Added detection of Net/Open/DragonFlyBSD

Release 0.2.1 - 19th January 2007

* Modification of graphing disply style
* Seperatation of device types
* Implementation of storage graphing

Release 0.2.0 - 20th December 2006

* Cleanup of graphing code
* Seperation of customer-accessible interface
* Preliminary alerting system

Release 0.1.2 - Late November 2006

* Graphing of additional server-related data

Release 0.1.1 - November 2006

* Removal of large amounts of perl

Release 0.1.0 - October 2006

* Initial Release
* Basic discovery in place. Graphing in place