My current/recent favorite apps:

- Pretty much all the Google-branded stuff. If I'm running in an unfamiliar location, for example, I'll use Google's My Tracks.

- My-Cast Weather Lite to put the current temperature in the status bar and a brief forecast in the drop-down. I used to use WeatherBug, but it had a habit of slamming my CPU.

- SoundHound: pretty good at recognizing random songs.

- DoubleTwist: seems to be a reasonable media player.

- Photoshop Express: useful for fixing contrast/brightness on images from the crappy camera in my phone prior to uploading them to Facebook or whatnot.

- Prey (part of the Prey Project) to recover my phone if it's lost or stolen.

- Swiftkey (which I switched to from Swype) - awesome predictive keyboard.

- Amazon's App Store: good for the freebies.

- Seesmic: useful for quickly posting the same status update to Facebook, Twitter, and Google Buzz in one go.

- RPN Calculator: free, does everything I want.

- Gentle Alarm: a freebie from Amazon, at one point. Very nice.

- PewPew 2: another Amazon freebie, at one point. Nice game.

- Galcon: addictive game (that I actually paid money for).

Root-only stuff:

- ClockSync: gets my phone on real atomic time, not whatever Verizon feeds me (which is often ten seconds off).

- Barnacle: tethering support.