Don't know what type of application you are going to be developing, but if it is web based, may I humbly recomend you take a look at PHP?
Take a trawl around various computer language sites for arguments for PHP e.g. www.developer.com .
PHP4 and mySQL are a doddle to install on OSX.
Whichever way you go, I too recomend the O'Reilley books.