It looks like there a few working solutions for using custom true type fonts (ttf) on the iPhone, most notably Can I embed a custom font in an iPhone application? However,
I had trouble with this, too. Here is what worked for me:
NSArray *names = [UIFont fontNamesForFamilyName:@"Foo";<__NSCFArray 0xe9c4da0>(
Foo-100Italic, Foo-100 )myLabel.font = [UIFont fontWithName:@"Foo-100Italic" size:24];