I just became an iPhone convert a few weeks before Christmas (of course I acted surprised on Xmas morning). There seem to be some real gems buried in the app store (along with a bunch of duds) that really extend the usability of the phone.

So far I've found that I use the following on a daily basis:

RTM (Remember the Milk) - I already had a pro account on the web so installing the app was a no brainier.

Google Apps - All the Google apps with Goog-411 added, with voice search to boot!

AP Mobile News - Nice little news reader with "local" story selection. AP stories only so I'm on the lookout for a decent RSS feedreader.

Readdle Take Note - Takes voice notes, written notes, picture notes, and drawn notes and allows transfer between the desktop via wireless folder.

Readdle Docs - Full featured document reader (PDF, .doc, .xls, etc....) that allows wireless transfer between desktop and phone.

EZ Writer - Landscape keyboard for email, still looking for landscape SMS keyboard.

Apps that are cool but I don't use everyday:

Urban Spoon - Location aware restaurant finder

Showtimes - Location Theater and Movie finder

US Constitution - All articles and Amendments with notes too.

Snap Tell - Find books, DVDs, and CDs online by snapping a picture with your phone. The app returns reviews, online vendors, wikipedia entries, and pricing and is frighteningly accurate.



That's what I've found useful so far, what iPhone apps do you use on a daily basis that make your iPhone a more functional device?