Something like these cocoa methods:
NSDictionary *dict = [NSDictionary dictionaryWithContentsOfFile: path]
[dict writeToFile: someOtherPath atomically: YES];
NSArray *array = [NSArray arrayWithContentsOfFile: path];
[array writeToFile: someOtherPath atomically: YES];
and so on. Ideally, the file format would be one I could create and edit manually.
EDIT: this is for Windows Phone 7.
EDIT: Thanks for the answers. Though looking through some of your links . . . XMLSerializer does not handle dictionaries?!?!?