ObjectiveKeychain is an Objective-C wrapper around Apple's Keychain Services for iOS. It allows you to easily save and retrieve items from the system's keychain.
Generic and Internet passwords are mostly functional. Better support for finding existing items needs to be added, and key/certificate support still needs to be added.
It's pretty simple to use:
InternetPassword *password = [[InternetPassword alloc] initWithLabel:@"My Internet Password"
accessGroup:nil];
password.account = @"my_username";
password.password = @"MySecr3tP@ssword";
password.server = @"www.apple.com";
password.protocol = kNetworkProtocolFTP;
[password writeToKeychain];