Instapaper's "read later" bookmarklet will change (for the better) how you consume content online. The iOS app is exactly what you need to read the content you've saved and nothing more. It's beautifully minimal.
Just wow. The developers of this little gem have almost ensured I'll never visit their website again.
I was hooked the first time I made some significant purchases while traveling 80+ mph down I-80. Massive value.
This app has tons of use cases, but the flight tracker alone makes it worth its weight in gold. Realtime updates on the status of your flights? Yes, please!
An addictive game akin to risk.
Best of breed SSH application. Perfect when you're in a pinch.
Seriously gorgeous interface for your Google Reader feeds. I literally wait until I'm around my iPad to check my RSS now. It's that good.
The best way to keep up with open-source activity on GitHub.
I'm sure you already know about Dropbox. Unsurprisingly, their iOS app is great too.
USA Today (iPad)
Even old people would ditch their paper versions of the USA Today if they had this application on hand. Sometimes I check up on the news just to use it.
Peruse and listen to tons of NPR content. So good.
Despite the constant Twitter API Errors, this is one of the best feeling Twitter clients I've ever used. It takes advantage of the iPad's form factor in every way.
Google Earth (iPad)
This app is nothing short of amazing. It literally puts the world in your hands as you tap, pinch, and spin the world around with ease. This is future stuff, and we are fortunate to be able to use such technologies.
Sorry for no direct links, but I was too lazy to fetch all the iTunes URLs for the apps. Just run a search in the App Store and you'll find them with no problem.
Do you have any iOS apps that you absolutely love? Please let me know as I'm always on the lookout for great software.