Struggling with applications that open certain extension files? For example opening mp3-files causes iTunes to open them default and copy the files to it’s own library.. Get RCDefaultApp http://www.rubicode.com/Software/RCDefaultApp/
Fast, simple mp3-player: Cog http://cogx.org/
LineIn is a simple application for OS X to enable the soft playthru of audio from input devices. In simpler terms, you can use LineIn to play sound coming in through a microphone or any other device plugged in to your Sound In port, just as was once available with OS 9’s “Play input through output device” option. http://rogueamoeba.com/freebies/
Text editor Smultron http://en.wikipedia.org/wiki/Smultron
Easy and simple DVD/CD burner http://burn-osx.sourceforge.net/Pages/English/home.html
Remember that OS X internal Preview can do lot’s of stuff for images, no need to find any application for basic image manipulation.