Hello, everybody!
Minecraft 1.5 is out and it's available for free here.

There's a lot of stuff that's been updated in this version.
Here's just a little of the massive changelog:
- BUG FIXES
 - Mobs can have custom names
 - Added Hopper (collects items and moves them to containers)
 - Added Dropper (similar to Dispensers, but always drops the item)
 - Added Activator Rail (activates TNT Minecarts)
 - Added Redstone Comparator (used in Redstone logic)
 - Smooth lighting now has three settings (none, minimal, maximum)
 - Some hostile mobs now are harder in Hard difficulty
 - More detailed death messages
 
Also, 2 new commands have been added:
- /scoreboard
 - /effect