MotionX GPS Drive ($1.99) - Turn-by-Turn voice assisted (but no text to speech, i.e. street names) navigation that seems to do a great job in most urban areas at a fraction of the TomTom app's cost
MotionX GPS Sport ($1.99, free for the lite edition) - GPS app w/ topos, waypoints, tracks that can be uploaded to twitter, facebook, etc. Nice little app. I use it primarily for my running and cycling around the neighborhood, but am anxious to try it out for dualsport riding once I buy a bike.
Mint.com (free) - Keep tabs on all of my bank accounts, credit card balances, mortgage, and retirement accounts in one easy to access tool. Also sends out alerts for over-budget warnings (I don't bother with the budget features) and large withdrawals or deposits.
Echofon (free) - Used to be called Twitterfon. Hands down the best twitter app that I've found, as it has photo and gps location attachments built in. A little buggy in the latest version, but still cheaper and better for my needs than Tweetie.
Lose It! (free) - Weight tracking and daily food diary. Unfortunately the food database isn't as comprehensive as some tools I've used in the past, but hey, it's free, and it's super easy to add new foods to the database.
Amazon.com (free) - Not much to say here, other than that it makes Amazon waaaay too easy to shop now. My impulse buys (particularly on books) have gone up quite a bit, as the one-click purchase button is oh-so-shiney and begs to be pushed.
Ragdoll Blast ($1.99, free for trial version) - Fun little physics based game. Some of the levels are damned frustrating, but its addictive enough that I pretty much played my way through all 140-some levels in the first day or two I had it.
Wordpress (free) - Update your wordpress based blog while on the move. Supports inline embedding of images. Sure, it's not as full featured as using the web-based editor, but it fits the bill for quick and easy posting - great if you're on the road.
Facebook (free) - Yeah, yeah...
Measures ($1.99 or 2.99, can't remember) - I lived in Germany for 18 months and having the currency conversion and unit conversion for everything from teaspoons to fl oz's to UK and EU shoes and shirt sizes was invaluable. It really is a fantastic program and the first one I ever paid for.
TheWeatherChannel (free) - Despite the ads, it's better than the built in weather app.
Pandora (free) - This alone was a life-changer. Hyperbole aside, it completely replaced the need for satellite radio for me and makes boring days at my desk behind a DoD firewalled internet connection much more tolerable. Even 8 gigs of mp3's gets old after a while, so the fresh mix of music is more than welcome.
-Erik