The easiest way I know is using a sortDescriptor:
// Sort the tags by name
NSSortDescriptor * firstDescriptor = [[[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES selector:@selector(caseInsensitiveCompare:)]
ascending:YES] autorelease];
NSArray * descriptors = [NSArray arrayWithObjects:firstDescriptor, nil];
NSArray * sortedArray = [tagsArray sortedArrayUsingDescriptors:descriptors];