iPhone Apps are what make the phone worthwhile. This is a list of Applications that I recommend:

• Stanza is a brilliant eBook reader. It allows over-the-air book downloading from places like Project Gutenberghttp://www.lexcycle.com/.
• Evernote stores notes you take on their servers, and performs OCR on embedded images. Great way of taking meeting minutes. http://www.evernote.com/about/download/iphone/.
• Shazam will identify songs for you that are playing nearby from a short sample. http://www.shazam.com/music/web/pages/iphone.html.
• Discover provides a flex-based interface on your phone so you can copy files from a PC or mac to the phone. http://www.148apps.com/reviews/discover/.
• There are tons of iPhone Apps for Twitter (tweetie is very popular), but I use Tweetdeck, because it syncs with the groups I have on my desktop. http://tweetdeck.com/iphone/.
• EirText Pro gives you webtexts on your phone. Well worth paying for, though there is a free one. http://www.vinnycoyne.com/lackofconcept/?page_id=80
• Dropship is a really fun little 3D shooter. http://toucharcade.com/2008/12/11/dropship-now-this-is-a-shooter/
• I Dig It is a version of DigDug. Incredibly addictive. http://www.inmotionsoftware.com/AppsGames/IDigIt.html

Also worth a look are the aggregate sites like 148apps,

More when I think of them.