The iPhone 4 brings a lot of new features, and this list of top 10 best free iPhone 4 apps will help you make the most of your new phone.

We’ve gathered up 10 of what we feel are the best applications in various categories to give you some guidance in what you should be taking up valuable space with on your iPhone 4. Communicate with friends, plan a better trip, play games, do business and more!

1. Shazam

Shazam is an app that feels like magic when you first use it. It's deceptively simple—hold your iPhone near to a music source, and wait while the app listens and tells you what track is playing. But the sheer technology behind this simplicity is mind-boggling, and while Shazam doesn't always guess right (and only allows five 'tags' per month for new users, unless you upgrade to the paid version), it's worth a download.

2. Google Earth

"Hold the world in the palm of your hand," says Google about Google Earth, which enables you to fly across the planet by swiping your finger. More integration with content and features from Maps would be good, but Google Earth's Wikipedia articles and a Panoramio layer at least ensure it's a great app for seeing the world from your living room.

3. eBay Mobile

Unsurprisingly, eBay also has the buying side of its operation covered with eBay Mobile. The app supports iOS 4 multitasking, and, like eBay Selling, it's fast and efficient, to the point that it's preferable to using eBay's website on a PC.

4. Red Laser

Now free, due to being snapped up by eBay, the Red Laser bar-code scanner is pretty accurate, even if you're still saddled with an iPhone 3G. It's great for checking prices while shopping, and also enables you to get your media collections into Delicious Library if you make use of AppleScript.

5. iBooks

Having made a big splash on the iPad, iBooks has now arrived for Apple's smaller devices. Effectively iTunes for books, the app combines a reader and store, in Apple's typically usable and integrated fashion. Usefully, iBooks includes PDF support and bookmarks automatically sync across devices.

6. Last.fm

Although Last.fm has been overshadowed by Spotify, the iPhone app's worth a download, due to it creating personalised radio stations based on your favourite artists or genres.

You might not get to hear precisely what you want, but chances are you'll discover new music that appeals.

7. Simplify Music 2

If you're annoyed at your device's meagre capacity and long for a 200GB iPhone, Simplify Music is the next best thing.

In tandem with a Simplify account, an app on your Mac or PC, and a Wi-Fi or 3G connection, you can access your (non-DRM) music from anywhere, along with streamed music from collections of up to 30 friends.

8. Internet Radio Box

If you can't be bothered splashing out on a DAB radio, plonk your iPhone into a dock, connect its audio output to some speakers, and play one of over 30,000 radio stations through Internet Radio Box.

Shake-to-shuffle is a nice touch, but all the important features are there, too, including favourites management, a configurable sleep timer, and the ability to play in locked mode.

9. PCalc Lite

"But I've already got a calculator on my device," you might argue. True, but now you can stash default Apple apps in a folder, it's easier to justify replacing them with something better - and PCalc Lite is without doubt the finest free calculator for iOS, with a great interface and plenty of options. You can also bolt-on features from the paid version via in-app purchases.

10. Instapaper Free

Set up an Instapaper account, create a bookmark in Safari on your device, and you can then send articles to Instapaper Free, for a superior and focussed offline reading experience. The app also acts as a superb taster for the paid version, which adds alternate themes and iPad support.

About Author

Henry, a computer science engineer engaged apple product research. You can get help on how to transfer music from iphone to computer, as well as transfer music from ipod to computer.