There are tons of applications both useful and gimmicky for the Touch Diamond. I found most of mine on here or on forum.xda-developers.com. The apps I use or have used are:
GPSed - allows you to track your routes via GPS whether by car, bike, boat, plane. You can view the routes online in Google maps via www.gpsed.com and you can attach photos to your journey by getting the software to tag your photos with GPS info (I haven't used the photo feature yet)
TCPMP - allows you to play all types of movie files
CameraAware - speed camera warnings and also allows you to track your routes
Diamond Hologram - virtual hologram using the gsensor
Diamond Cubes - dice rolling
Diamond Beer - simulates a glass of beer
Manila Customizer - allows you to change icons on TouchFlo3d with a simple user interface
WalkingHotSpot - use your phone as a wireless access point
Google Maps
TomTom
Nav4All - free GPS navigation but very basic - no map view while driving and voices aren't very clear
GRemote - use your phone wirelessly as a touchpad, gsensor enabled mouse, game controller, keyboard or media remote for your PC
Batti
AnswerkeysDisabler - stops you accidentally answering when in your pocket
Gsensor calibrator, Total Commander, FDCsoft TaskManager, Vibratealert, ING Font Change, AdvancedConfig and TF3D config for more customising
Capsure - screen captures from device
MyMobiler - allows to control device from PC and record videos and screenshots of the device in action
PocketGForce - measure GForce's using Gsensor (can't imagine it is very accurate)
Note2Self - dictation that is automatically sent to your email
Glight - control brightness of screen using light sensor
RemoteTrackerConfig - haven't tried yet but is location based security based on GPS or GSM cells so you can find your phone if it's lost or stolen
Pedometer - haven't tried yet
I'm sure there is more but I can't remember them all. Try here:
http://www.modaco.co...amond-software/ and here for gsensor apps:
http://forum.xda-dev...ad.php?t=430541