The next version of Apple's Macintosh operating system - Mac OS X 10.5 Leopard - is finally on the loose... and finding its way into the hands of Mac fans across the globe.

The Mac web is awash with fans giving their first impressions, and they're raving over many of the less well-known new features. The Unofficial Apple Weblog (TUAW), for example, is running a series of features on Ruby on Rails, Core Animation, Hot Spots, iChat screen sharing and Web Clips, among others. Here's a quick overview while we wait for our copy of Leopard to arrive:

Ruby On Rails - this web development application is now built into Leopard making it easy to program your own web apps. Ruby on Rails has been highly praised in Web 2.0 circles. It's native to the Mac and it's free.

Core Animation - a unique animation framework built into Leopard that promises to make applications funkier, easier and more fun to use. Mac developers are expected to make extensive use of Core Animation in the coming months

Hot Spots - Leopard's universal access controls enable your Mac to monitor different parts of the screen, and then alert you if anything interesting happens. TUAW isn't sure if Hot Spots is in the shipping version, but it could be handy for downloading files or keeping tabs on other apps, it says.

iChat Screen Sharing - this nifty feature enables you to rummage around on another Leopard user's Mac while you're both having video chat. You'll need the other user's permission to do this, of course. But this could be great for collaborating on work documents like Excel spreadsheets, presentations and so on.

Web Clips - so your favourite site doesn't have a Widget? Well create your own - instantly - with the Web Clip app in the Leopard version of Safari.

More cool Leopard features

David Pogue of the New York Times has also picked of some of his favourite features in Leopard - stuff he didn't have space for the in the review we featured yesterday.

He says its easy to find sometimes deeply buried features in applications using Spotlight - Mac OS X's desktop search tool. While in the application, you simply type the command you're trying to find, and Leopard picks out the nearest match with an arrow to show you where it's hiding.

He also likes the fact that Dictionary words and even a Calculator are also located in Spotlight, saving you the hassle of actually opening the apps. To trigger them press Command-Space and just start typing - if it's a word, the dictionary definition will pop up; if it's a sum, Spotlight will do the calculation for you. How cool is that?

Spotlight can even help you launch applications. Press Command-Space again and start typing the name of the app - bingo! Instant results. Just press Return / Enter to launch the app that pops up.

More Leopard news and analysis coming this way soon.