Ok, so I've been learning Mac programming using Objective-C. I'm still a horrible rank amateur at this stuff, but here's one thing I've learned. Here is an example of how to display a modal File Open dialog box...

int i; // Loop counter.

// Create the File Open Dialog class.
NSOpenPanel* openDlg = [NSOpenPanel openPanel];

// Enable the selection of files in the dialog.
[openDlg setCanChooseFiles:YES];

// Enable the selection of directories in the dialog.
[openDlg setCanChooseDirectories:YES];

// Display the dialog.  If the OK button was pressed,
// process the files.
if ( [openDlg runModalForDirectory:nil file:nil] == NSOKButton )
{
    // Get an array containing the full filenames of all
    // files and directories selected.
    NSArray* files = [openDlg filenames];

    // Loop through all the files and process them.
    for( i = 0; i < [files count]; i++ )
    {
        NSString* fileName = [files objectAtIndex:i];

        // Do something with the filename.
    }
}