Number one app for us is Graphic Converter:
http://www.versiontracker.com/dyn/moreinfo/macosx/11559
It opens up graphics that photoshop chokes on! I even had a .psd file that photoshop wouldn't open but Graphic Converter did. Export options are huge.
Number two application is JellyFiSSH:
http://www.versiontracker.com/dyn/moreinfo/macosx/11282
Gives us quick access through terminal. I use this to clean up any unwanted email that doesn't get removed by the email programs such as Eudora. For some reason they don't delete all the emails after download, just some.
Number three is a shameless plug :wink: for one of my own products as seen on Ten for X games by Allume Systems:
http://www.versiontracker.com/dyn/moreinfo/macosx/16180
