1. Download MC executable jar file from http://minecraft.net/download.jsp (Under Linux/Other heading) and save it to /Users/yourusername/Library/Application Support/minecraft/bin/LaunchMinecraft.jar
2. Open AppleScript Editior in Applications->Utilities
3. Type (change theproxyserver.com and theproxyport to your settings):
do shell script "java -Dhttp.proxyHost=theproxyserver.com -Dhttp.proxyPort=theproxyport -Xmx800m -jar '/Users/yourusername/Library/Application Support/minecraft/bin/LaunchMinecraft.jar'"4. Save as LaunchMC.app and run this instead of the Minecraft.app launcher
5. Profit ????
Here's how to do it on Windows too.. http://www.blankmind...behind-a-proxy/