Developers have flocked to Apple’s iPhone SDK, but there is a significant barrier to entry: knowledge of Objective-C, the programming language that is used to build native iPhone apps.

Fortunately, cooking up a hot iPhone app doesn’t require you to get too geeky. Developers who don’t know Objective-C, or who don’t want to learn yet another programming language, can build native iPhone apps using these five tools.

Titanium Mobile

If you know HTML/CSS and JavaScript, you can build native iPhone apps (and Android apps) using Appcelerator’s Titanium Mobile development platform. The Titanium Mobile APIs provide developers with access to iPhone features such as the accelerometer and filesystem, as well as third-party services like Facebook.

Price: Free

Corona

Corona enables developers to build native iPhone apps using a proprietary language that Ansca Mobile, the company behind Corona, bills as being ”easier than writing Javascript or ActionScript“. Like Titanium Mobile, the Corona SDK gives developers access to iPhone functionality such as GPS and the camera.

Price: $99 (“special introductory price”)

PhoneGap

PhoneGap is another development platform worth looking at if you’re familiar with HTML/CSS and JavaScript. In the past, there were some issues with PhoneGap apps being rejected by Apple, but that has since been resolved and apps built with PhoneGap are apparently officially welcomed for consideration.

Price: Free

Rhodes

If your programming language of choice is Ruby, Rhodes may be just what you’re looking for. It’s an open source framework for building native mobile applications, including native iPhone apps, that relies on HTML and Ruby.

Price: free for open sourced apps, $500 per commercial app

Flash

The iPhone may not support Flash, but that doesn’t mean that you won’t soon be able to build native iPhone apps using it. Adobe Flash CS5, which is currently in private beta, will include a new feature called Packager for iPhone. As the name implies, the Packager will let Flash developers package their Flash projects for the iPhone.

Price: To Be Announced