Each month, the best new iPhone apps—and some older ones—are considered for admission into Gizmodo's Essential iPhone Apps Directory. Who will join? Who will live? Who will die?

The Month's Best

Layar: There's the obvious reason to be excited about this:

Layar, the first camera-based AR app to really blow us (or anyone) away, has quietly slipped into the App Store. As with the Android version, the app overlays all kinds of information onto a live view of the world around you.

And the less obvious, but ultimately more important one: Layar layers, which let you install user-generated overlays of all different kinds of information, like this one, which tracks government bailout spending. Free.

Tweetie 2: From Matt's review:

It's the most polished Twitter app yet, oozing slickness with every swipe. Yet, it's exploding with new features, and still really fast. It manages to cram in every possible feature you could possibly want in a Twitter app-offline reading!-without feeling too complicated or bloated.

It's three dollars, even if you had the previous version, but totally worth it.

Photoshop: To call this app Photoshop is almost a misnomer—you can't have anything resembling desktop Photoshop on the iPhone, but you can have a decent photo processing app:

The tools are basic-you can crop, adjust exposure, saturation, and tint, among others, with some standard special effects like soft focus, colors and filters like "warm vintage" and pop-but using entirely swipe-based gestures as a virtual slider for how intensely or lightly the effect is applied is natural and easy

This, combined with ties to an online service and the fact that this, unlike almost any other similar app, is free, make it a must-download.

MotionX GPS Drive: At $3 a month without any kind of long-term commitment, this is currently the cheapest decent turn-by-turn app in the App Store. And it works, pretty well! Until Google Navigation for Maps hits the iPhone, this'll be the cheapest, least-risky turn-by-turn option out there.

NASA: Pure, welcome information overload for space geeks, in an app. NASA's really been killing it with their online strategy lately—lots of news, downloadable media and Twitter action—and this app is a wonderful extension.

Squareball: If Pong grew into a platformer, or Breakout into a sidescroller. You can pick it up quickly, but it gets progressively harder over time without ever getting frustrating. In other words, it's pretty close to a perfect game. Try the free demo before dropping the two dollars though, since with its retro graphics and soundtrack, dead-simple gameplay concept and fast face, this one can be polarizing.

Rock Band: It's not perfect—controls can be awkward, and the singing mode isn't really a singing mode, but it represents the first major rhythm franchise to hit the iPhone, and it bear gifts: Great graphics, decent, familiar, song selection, and multiple instruments.

NASDAQ: It's much more intensive that the stock stock (stock stock stock) app, and comes with StockTwits integration, which provides a little crowd-sources insight to go along with your stream of numbers. Best of all, it's free.

ReelDirector: This is as close as you're going to get to iMovie on your iPhone. (Which isn't very close, to be honest!) Video stitching alone, will be worth the ($8) price of entry for many people, but keep in mind that Apple instantly render this app obsolete if they just built decent editing into their OS.

Nikon Learn and Explore: It's heavily branded and obviously intended to promote the Nikon name, but hey who cares: Nikon's Learn and Explore app is actually a great, free photography primer no matter what kind of camera you carry.

App Directory Inductees

So, who will join the illustrious ranks of Gizmodo's Essential iPhone apps? I've sifted through user submissions, app updates and new arrivals to find our newest inductees:

• MotionX Drive, for its brilliant value-to-functionality ratio.

• Photoshop, for undercutting almost all of the overcrowded, underinnovating photo app field with something decent and free.

• Layar, for being a free, solid platform for augmented reality on the iPhone, which will be made great by new layers.

• Tweetie 2, for being even better than it was before, and for being the best iPhone Twitter app out there, assuming you're willing to shell out a few bucks.

• Instapaper, for its tragic exclusion in the last update: the ability to save pages for offline reading is useful for just about anyone, but absolutely essential if you're a frequent flyer or subway rat.

• Runkeeper, for simultaneously offering the most feature-complete outdoor exercise app I've seen in a while and offering a decent free version as well.

• Backgrounder, a jailbreak app, for giving everyone a taste of what a multitasking iPhone is like. (Hint: pretty great)

And Farewell To...

• Twitterfon, not because it's bad—it's still the best free Twitter app, but because it's not called Twitterfon anymore. Hello, Echofon.

• TomTom, because Navigon has done more to innovate in the last few months, and because with great, cheap options nipping at their heels, expensive iPhone apps like this are harder to justify.

• Tweetie, for you have been replaced; cannibalized by your own child.

• CameraBag, for being two whole dollars more than Photoshop. (Sorry!)

What counts as an essential iPhone app changes all the time, and so should our guide: If we've missed anything huge, or you've got a much better suggestion for a particular type of app, let us know, or say so in the comments. We'll be updating this thing pretty frequently, and a million Gizmodo readers can do a better job at sorting through the app mess than a single Gizmodo editor. Enjoy!

[Gizmodo's Essential iPhone Apps]