iOS4 apps: Amazon.com, WebMD, SimplyTweet, Mapquest, Audible

It's been a while since our last iOS 4 compatible apps roundup so we figured it was time for another.  I've seen quite a few updates come through in the past week or so but here's the ones that caught my eye the most.  And as always, if you see any you think are above the curve, let us know in the comments!

Keep reading to see what's been added this time!

Amazon.com App

Amazon has a pretty appealing iPhone app. I frequently browse it on my iPhone while laying in bed or when I'm sitting somewhere bored. You can not only browse, but manage your account and purchase things. The entire process is pretty simple. Amazon has now added high resolution images to support the iPhone 4's retina display. Best of all, the app's free.

[iTunes Link]

SimplyTweet 3

SimplyTweet has long been at the top of my list for great Twitter clients. This time around, it got even better. Their update for iOS4 is probably one of the largest I have seen. They've not only added resolution enhancement for iPhone 4, but background uploading, fast app switching, and several other features. This update also seems to fix a lot of bugs. If you're looking for a more than decent Twitter client and don't mind dropping around $5, SimplyTweet is right up there with Osfoora and Twitter for iPhone.

[iTunes Link]

Mapquest 4 Mobile

There's a lot of quality navigation apps out there, but for some of them, you'll spend a pretty penny. Mapquest 4 Mobile is a very decent GPS app that won't cost you anything. It's been updated to support background voice navigation under iOS4. It's also a very decent app to view common things such as restaurants, gas stations, coffee shops, schools, etc.. I've used it for a few weeks now and it suits my navigation needs just fine. If you haven't tried it yet, it's free to check it out!

[iTunes Link]

WebMD

WebMD is an incredibly useful tool for looking up a lot of medical issues all in one place. It has features such as a symptom checker, treatment recommendations, and my favorite feature, the pill identification tool. If you've ever found random pills in a drawer or the label is peeled off, odds are you can probably narrow it down to a few with this. I'm not exactly sure what all WebMD has added but I'm pretty sure fast app switching is now working (assuming they aren't just caching like some apps did under 3.x), and it seems to look a little better on the iPhone 4 than it did before. I'm not 100% on this so if anyone knows for sure, drop it in the comments!

[iTunes Link]

Audible

Audible is a great site (and app) to access your digital audiobooks. Once you have an account, you simply sign into the app and it'll show what you have available. It also gives you a few choices for new users for free (not that great of a selection, but there is some). The app is free and now supports feature in iOS4 such as background downloading and background playback, which is awesome for those of you who want to listen to a book while being able to do other things on your iPhone. It's a free download in the app store so if you are an audiobook fan, go and grab it!

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[iTunes Link]

Those were our favorites, if you guys have some, drop 'em in the comments for us!