Dropbox

We rave about Dropbox all the time at Wired.com. That’s because it’s an indispensable addition to the iPad. It is an online storage service that works on an iPad, iPhone, Android phone, or any Windows or Mac PC. Your Dropbox folder is where you put all the files you want to access with any device, and the service automatically syncs so they’re available to you everywhere.

Say, for example, that you’re a student with a Mac and you want to read research papers on any of your devices. On your Mac, drop some PDFs in your Dropbox folder, then on the iPad launch the Dropbox app and you can read those PDFs on the tablet while you’re on the bus. You could also launch the PDFs with the Dropbox app on an Android smartphone or iPhone.

Besides PDFs, you can put video, pictures and music in your Dropbox, too. You have to have this app: It’ll save you a ton of time that you’d otherwise waste syncing to iTunes over USB.

Free, download link.

Air Video

Let’s say you’ve got a lot of video files on your PC that aren’t iTunes-compatible, or were acquired through (ahem) less than legal means. With AirVideo, you can quickly set up a server on your PC and choose a folder that you want to share with your iPad.

Then hop on your iPad and launch AirVideo, and you can instantly stream most videos inside that folder. AirVideo will even live-convert videos while you’re watching, so it’s all an instant, seamless experience.

$3, download link.

Friendly

There isn’t an official Facebook app made just for the iPad. Until Facebook comes up with something better, Friendly is basically the best option.

It’s polished and its looks resemble Facebook’s own style, so you’ll feel right at home. After you log in with your Facebook ID, you’ll be wasting time stalking your Facebook buddies in no time.

Free, download link.

GarageBand

Made by Apple, the GarageBand app is simply stunning. The app packs a virtual piano, guitar, bass guitar and drum set to record songs.

Especially neat are Apple’s “Smart” instruments, which contain preset chords and rhythms for each instrument, so anything you play can sound good. This way, people of all ages will be able to pick up an iPad and compose some neat tunes.

$5, download link.

Infinity Blade

Originally made for the iPhone, Infinity Blade has been rescaled and beefed up for the iPad. While it works on the first-generation iPad, it’s even better on the iPad 2.

This 3-D sword-fighting game puts the iPad 2’s powerful graphics processor to good use. Swipe your fingers on the touchscreen to attack, parry or dodge. It’s a superfun game that should provide hours of entertainment.

$6, download link

Instapaper

We’ve featured Instapaper before, but we have to mention it again, because it’s just too crucial. Reading through a web browser can be a chore, with all those distracting ads, ugly sidebars, etc.

Hit Instapaper’s “Read Later” button on your PC web browser to add a page to your reading list. Then on your iPad you can launch the Instapaper app to read everything you’ve saved with just the words and pictures, stripped of all the junk.

It’s great for concentrating, and it might just change the way you read.

$5, download link.

Flipboard

We can’t get enough of Flipboard, a beautiful social magazine. Fundamentally, it scrapes content from URLs shared on Twitter, Facebook and RSS feeds.

But that doesn’t do justice to the elegant way it lays out the stories for easy browsing. It’s even better on the iPad 2 now because of the performance boost.

Wired.com is an official partner of Flipboard, too, so you’ll notice our site’s content has been optimized for Flipboard.

Free, download link.

PenUltimate

If you come up with a great idea, you can quickly jot it down in this note-taking app that acts a a virtual Field Notes notepad. Unlike other note apps, where you have to type, PenUltimate just lets you scribble on the screen with your finger (or a stylus).

We love it because the design and overall feel of the app is just slick.

$2, download link.

TuneInRadio

Listen to all your favorite online radio stations with this app. Plus, you can use this app to set an alarm to play your favorite station in the morning.

As there’s no built-in alarm app on the iPad, this should come handy. Sure, you’ve just turned your iPad into a $500 clock radio, but you can’t pick up the clock radio and read Google News on it, too, can you?

$1, download link.

World of Goo

This cutesy puzzle game involves stretching black blobs of goo at geometric angles to reach a goal point (a pipe that sucks up the goo). The sharp graphics and clever sound effects are a nice treat for a game that challenges your noggin.

$5, download link.