Apple’s “Rock and Roll” event in San Francisco today wasn’t all about the iPod and the return of the company’s famous CEO to the stage. The company also unveiled an iPhone 3.1 software update, along with iTunes 9.

The iPhone update is designed to offer new features and fix bugs. Apple says it has applied its Genius technology for apps, so recommendations will automatically appear based on apps the user already owns.

Apple also added ringtones from major labels. The iTunes Store on iPhone now features pre-cut ringtone downloads with more than 20,000 ringtones priced at $1.29.

The additional features were welcomed by the likes of AdMob, whose ad network reached more than 20 million unique iPhone and iPod touch devices in August.

“The new Genius recommendation engine for apps and enhanced organization and sync capabilities will give developers increased discoverability and distribution of their apps, offering more opportunities for monetization and engaging with iPhone and iPod users,” said Jason Spero, AdMob vice president and managing director/North America, in a statement.

The iPhone 3.1 is available now as a free download from iTunes for 3.0 users.

Of course, Apple CEO Steve Jobs received a standing ovation when he took the stage. Jobs, who underwent a liver transplant in the spring, urged the audience to become organ donors.