I'm trying to run Fluenz on my computer and it's a .osx file. When I try to open it, it opens in Textmate. Kind of odd. Does anyone know how to restore its original default program? I think that I might have changed all .osx files to open in Textmate some time in the past for a programming project, but I don't know what the original was.
There is no real default program, as the file type is apparently not known by OS X (at least on my system). It depends on the applications you installed on your system.
You can always right-click and select Open With… to see which applications claim support the file type. If the desired program is in the list, you can Get Info the file, and then change the program to use for opening all files of this kind. This setting is in the Open with section by selecting it and then pressing Change All….
To remove the custom association with TextMate, remove the matching entry from