From Mac Guides
Leopard is the codename for Mac OS X 10.5. The codename was announced at WWDC 2005, and Apple previewed the operating system at WWDC 2006 on August 7.
Leopard began shipping on October 26, 2007 at 6 PM  for $129 USD, after being delayed from an initial target of Spring 2007 (northern hemisphere) . A full preview copy was given to attendees of WWDC 2007. It was announced at Macworld San Francisco 2008 that 5 million copies of Leopard were sold in the first 3 months after release.
High resolution promotional screenshots of Leopard
Leopard had over 300 new features.Some notable features are:
- Time Machine for automatic backups and for viewing old versions of files
- Boot Camp, Front Row, Photo Booth all bundled with Mac OS X
- Spaces - Virtual desktop support
- Improved Spotlight
- Core Animation
- New features in Mail
- Web Clip for Dashboard and Dashcode for developers to developer Dashboard widgets
- Enhanced iChat, with multiple logins, better audio quality, visibility, animated icons, video recording, tabbed chats, Photo Booth effects and "iChat theater"
- New Universal Access with enhanced parental controls and much improved text to speech that sounds more like a real person
- Multiuser iCal
- Xcode 3.0 and Interface Builder 3.0
- Full support for 64 bit applications while maintaining 32 bit support. Leopard would be the first mainstream operating system to go completely 64-bit.
- A new desktop interface, including a new translucent menu bar, a new reflective Dock, a new feature called stacks to cleanup the desktop, a consistent window look (no more brushed metal) and a prominent active window
- A new Finder, with an improved sidebar, searching of other computers, shared computers, "Back to my Mac" to connect to computers not on the same LAN using .Mac, and an iTunes-like Cover Flow view
- Quick Look, which gives live file previews
- A new Movie Times widget and new features in Web Clip
These features were part of Apple marketing (website, WWDC) or were present in developer builds, but have not been delivered as of 10.5.3:
- Support for Airport Drives in Time Machine (was present in developer builds)
- Answering Machine from iChat
- Fast OS switching 
- R2D2 effect from iChat
- Notes sync option with iPhone
- Resolution Independence
At the time of launch, several applications were incompatible with Leopard.
- A piece of Mac OS X malware, OSX/Leap-A, claimed to be screenshots of Leopard. Some say it was the first Mac OS X virus, although its classification as a virus is debated.
- 10.5.0 - October 26, 2007 
- 10.5.1 - November 15, 2007 
- 10.5.2 - February 10, 2008 
- 10.5.3 - May 28, 2008 
- 10.5.4 - June 30, 2008 
- 10.5.5 - September 15, 2008 
- 10.5.6 - December 15, 2008 
- 10.5.7 - May 12, 2009 
- 10.5.8 - Aug 5, 2009 
|Mac OS Versions|
Classic (prior to Mac OS X) | Mac OS X (Pre-release) | Mac OS X 10.0 (Cheetah) | Mac OS X 10.1 (Puma) | Mac OS X 10.2 (Jaguar) | Mac OS X 10.3 (Panther) | Mac OS X 10.4 (Tiger) | Mac OS X 10.5 (Leopard) | Mac OS X 10.6 (Snow Leopard) | OS X 10.7 (Lion)