A few random tips.
Use Command-Option-Escape to kill off unruly apps.
Install X11 to get access to a bunch of apps that run under the (Unix) X11 system. Should be on the developer tools disk, I think.
Then, install MacGimp. Poor man’s photoshop … but the price is right (free)
I like Smultron as a text editor.
Every once in a while, run disk utility (applications / utilities) and “repair permissions”. This will chase away some gremlins.
Install Darwin for occasional use of Windows apps without needing to install Windows. http://sourceforge.net/projects/darwine/