Smoke Glass dock.

Navigate to /System/Library/CoreServices

Right-click on Dock and 'show package contents'.

Navigate to /Contents/Resources/

Back up:

scurve-l.png

scurve-m.png

scurve-sm.png

scurve-xl.png

Then, replace them with these files.

scurve-l.png

scurve-m.png

scurve-sm.png

scurve-xl.png

You may have an issue with one of the files (scurve-xl.png I believe) not copying properly, if this happens, the original file needs to be deleted from the directory first.

Then open Terminal and type 'killall Dock' to restart the dock.

Ta-da! Much nicer.

Edit: Here are the original files if you forget to backup.

Credit: echobucket of SomethingAwful