For the developers:
http://www.mono-project.com/Mono:OSX
http://developer.apple.com/technotes/tn2004/tn2124.html
http://www.apple.com/applescript/index.html For using AppleScript from Apple.
Also check out man leaks and Instruments.app.

Look into smbclient.

How to use launchd and launchctl:
http://lingon.sourceforge.net/
http://www.informationdelight.info/encyclopedia/entry/Launchd
http://www.opensource.apple.com/darwinsource/projects/other/launchd-152/...

Here is a site for tips:
http://www.mactips.org/

Here are sites for anti virus:
http://www.clamxav.com/
http://www.clamav.net/