Have all of the below on my Sony X10.
2010 World Cup - good enough, redundant in 10 days time
Advanced Task Killer - Good
Album Art Grabber - Excellent at what it does
Alice - Usefull, sometimes. Syncs with the music on your phone and then returns gigs for the artists. Can set a filter for distance (e.g. return gigs within 50 miles).
Beeb Player - Looks like everyone has found this little gem
XE Currency - Simple and decent.
Facebook
Facebook Sync - Sync FB contacts with phone contacts and displays their FB picture in your contact list.
Goggles - Take a picture with your camera phone and this app searches for a match in Google and returns normal search results.
Kaloer Clock - Big digital alarm clock function and display.
Last.fm - Radio
Maps - Google Maps. Excellent. Recent upgrade now has decent navigation that I have used as sat nav in the car succesfully.
Mobicast - Cric info. Cricket scores live as with the ESPN website.
Music Junk - Download free music
Opera Mini 5 - Web browser, seems decent enough and good speeds... I still tend to lean towards the default.
Robo Defense - Quality little tower game. Addictive.
Soccer Livescore - Scores from all over the World. Ability to filter and mark faves etc.
Tweet Caster - Twitter
Weather Bug - Weather
Whats On - TV guide