Navigation
Navigation is in the latest maps update, it even manages to start before telling me my location is not yet supported, its coming. The impatient can look for the hacked maps app and use it now.
Titanium Backup is the essential app backup tool for rooted phones.
Cant believe no SMS replacements were listed, Handcents this weeks favourite, since ChompSMS went too far with the adverts.
Screeble: orientation and motion controlled override for sleep, seriously extends battery life by allowing much more aggressive sleep timeouts. I like my G1 running for more than a day.
I'd love to suggest an alternative to Fring, with its atrocious UI but its the only app where SIP 'just works'.
Of course the ultimate 'app' is a new rooted firmware, more speed, more apps, more choice.