More than 500 million apps have been downloaded through iTunes. The popularity of Apple's Apps Store is no surprise. Apps can really expand your iPhone's or iPod Touch's abilities.

Apps are small programs that run on the iPhone or iPod Touch. There are apps for almost anything you desire. Most cost a few dollars; others are free. Here are some of my favorite free apps.

EVERNOTE

Need to take notes on the go? Apple installs a note program on the iPhone and Touch. But Evernote is more flexible. You can upload notes using your computer via Evernote's site. This is perfect for long notes.

You can also create new notes from your iPhone or Touch. Notes aren't limited to text. You can create voice or photo notes.

GOOGLE EARTH

Google Earth will help you find directions and local attractions on the go. It also provides satellite imagery and topographical details. Or view relevant panoramic photos and Wikipedia entries. It's easier to navigate than the built-in Maps application. For example, Google Earth responds when you tilt your phone or Touch.

PHOTO APPS

PanoLab lets you create panoramas from up to 30 images. Take new images or use ones already on your iPhone or Touch. Perspective is automatically corrected.

Your photos aren't always flawless. SP Photo Fix Lite can help. It corrects white balance, adjusts contrast, applies filters and more.

Sharing photos is easier said than done with the iPhone and Touch. That is, unless you use PixUp. It uploads photos to Flickr, Picasa or Facebook. You can even assign location data from the iPhone's GPS.

MUSIC APPS

The iPhone and Touch can connect to your music at home or on the go. Apple Remote works over your home Wi-Fi network. It lets you control iTunes running on your computer.

Your entire music collection may not fit on your iPhone or Touch. So, Simplify lets you access your home iTunes library wherever you are.

BACKGROUNDS

Spruce up your iPhone or Touch with new wallpaper. Backgrounds offers more than 50,000 high-quality wallpapers with new ones added daily. Wallpapers are divided into categories for easy browsing.

BIG OVEN

Big Oven is great in the kitchen or at the grocery store. It puts thousands of recipes at your fingertips. Enter an ingredient to find recipes. Save your favorites and access them anywhere.

FINANCE APPS

Mint helps you track your account balances. You can also create a monthly budget and see how you're spending money.

A Personal Assistant isn't limited to bank accounts. You can also view social-networking, shopping and e-mail accounts. All of your information is protected with one master password.

SHOPPING APPS

Snaptell helps you check prices and find online reviews. Just snap a photo of a movie, book or CD. Snaptell provides links to reviews. You'll also get local and online prices.

Sale Price calculates discounts in dollars. Enter the amount of the item. Then, enter the percentage off. You can even use it to calculate an additional percentage off.

GPS APPS (IPHONE ONLY)

InstaMapper tracks your location through GPS. So, friends and family can follow you while you travel. Sure, InstaMapper raises privacy concerns. But it can be a great safety tool.

With Beacon, you'll never get lost. Just drop a beacon before you set out on a trip. The program guides you back to your starting point. It's handy for finding your car in crowded parking lots.

FITNESS APPS

Lose It! records your workouts and food intake. Your net caloric intake is updated automatically. You can also track your intake of fiber, protein and carbs.

StepTrakLite is a simple pedometer. It records your footsteps and times your workouts, categorizing them as moderate or vigorous.

Your iPhone or Touch isn't all work and no play. The most popular apps are probably games. You'll find action and driving games, puzzles and much more. There is something to suit every taste.