I do not know what I did before iPhone. Apparently many others feel the same as Apple is approaching a billion app downloads. In honor of the impending milestone I am making a list of my faves. Here they are - not in order...
Tweetie - one of many Twitter apps available. It is straightforward and easy to navigate.
Shazam - not only can it listen to songs (on the radio, cd's, etc.) and identify them, but then you are linked to performances on YouTube and links to iTunes to purchase.
SnapTell - take a picture with your phone of any book, DVD, CD and within get a rating, desription and links to Google, YouTube, Wikipedia, etc. Handy for comparison shopping and for remembering items that you see.
iNeedStuff - My favorite shopping list. Add items that you need to the list. When you use it to shop the geolocator feature of the iPhone identifies the store where you are and the application learns what items are where in the store. There is a desktop application so you can sync your phone to that master list.
NowPlaying - what movies are on? Also geolocates.
Games - Drop7 and Wurdle - I was completely addicted to Drop7 (described as tetris meets sudoku) until I played Wurdle. I have spent countless hours trying to beat my scores on both games.
Amazon Kindle - Book reader for the iPhone. I can access all of my Kindle books from my iPhone and it syncs to the last page I read on my Kindle! And vice versa.
Tipulator - figures tip amount on a check and can split the check, too.
Evernote - Helps you remember anything in your life. Notes, photos, recordings. I use it to capture web snippets, tweets, wine labels, where I left my car at the airport, directons, loyalty program numbers (who really carries all of those cards), emails, receipts, recipes, restaurants. Makes my life searchable. Syncs to the cloud and to my desktop. Word recognition makes all searchable. In conjunction with the Griffin Clarifi case you can get good photos of business cards (for instance) and have them all searchable in Evernote.