Mojang have released the latest Minecraft update, 1.4.4 containing tons of bugfixes that have affected 1.4.2. 1.4.3 was not released due to major issues that have since been resolved. It is available for download via the Minecraft launcher. Some of the more notable fixes are:
- Notable: Random falling damage due to lag fixed
- Notable: Falling damage when riding minecarts fixed
- Notable: Enchanted book exploit fixed
- Notable: Slimes have correct collision box
- Notable: Signs no longer lose their text client-side
You can find out more here. If you notice a bug, you can feel free to report it on Mojang's new bug tracking site. This should be the final release for 1.4, but stay tuned for more information about 1.5 and more.