Sign up for a free apple developer account at connect.apple.com, and download the Developer Tools. You can code in C/C++/Objective-C, Java or AppleScript.
You might want to check out RealBasic, too. It's about as close to VB as you can get on a Mac. It's not free, but it's much cheaper than most current versions of VB. They have a demo version you can try for 30 days to see if you like it.