Here is what I have installed on my Desire.
3G Watchdog - to track mobile internet usage and quotas
Advanced Task Killer Free - Don't use it for autokill. Just there in case something doesn't close properly.
Astro - File manager
Bookmarks to SD - plugin to backup bookmarks to SD card
ConvertPad - Unit converter. Helpful, since I live overseas.
Dolphin Browser HD - I tried lots and I just prefer the ability to switch tabs easily in this one. Not perfect though.
LED Lite - Lights up the flash bulb on the Desire's camera. Very bright and comes in handy.
Goggles - For barcodes or just to play with.
Google Pinyin - Chinese input
Hanping CE - The best free Chinese dictionary I have found that stores on SD card - does not require web.
Lookout - Security and lost phone recovery.
MapDroyd - Download maps to store on SD card. Not as good as Google maps, but nice to have an offline version.
MLB.com At Bat
My Maps Editor - links to Google Maps, so I can create maps on my computer of places I want to go or plan a trip, and sync easily to the phone
Nesoid / SNesoid /Toss It / Solo Lite / Mahjong - to kill boredom
HTC Notes widget - I like that I can type or draw with my finger
Places Directory (Google) - better than a phone book
Screen Cut - Dolphin plugin to let me save screen shots of webpages for viewing later
Tasker - I am playing with the trial. I'm not thrilled with it but like the idea of having things turn on and off based on location/other parameters.
Voice Recorder - Handy for meetings or other things
Wifi Analyzer - Great for analyzing your home wifi (or your friends)
XiiaLive Lite - Not able to get Pandora here. This is the best similar thing I've found. Uses Shoutcast streams.
Edit - Recently added the following that I would also recommend:
SMS Translate: Automatically translates SMS received in another language using Google Translate. (Awesome for me, since my mobile provider and bank often send me SMS in Chinese.)
Startup Cleaner Pro: Let's me prevent applications (including stock apps) from loading at startup. Increased my boot speed quite a bit once I removed things that I only need to use when I open them (or don't use at all).
Flycast: Lets me listen to WAAF or WEEI on my phone. (Maybe not a big deal for you, but cool to have in China).
Edited by amlothi, 18 July 2010 - 08:48 AM.