I would say the top 5 i use every day are..
DroidLive - A shoutcast streamer that lets me listen to a few select awesome web stations.
Evernote - any time i need to remember something, i either take a photo or write it down and evernote stores it in the cloud so that when i get home its there for me.
Nimbuzz - it combines facebook, aim and gtalk
PhonemyPC - i just started using this but its amazing that you can have that much control over your computer remotely.
TorrentFu - nothing like scanning a cd at a store and coming home and it being ready to listen to.