Mine are: Gmail, Day One, Twitter, Starbucks and Dropcam.
Odd list, perhaps. Still ploughing away with the N900, overclocking it on every reboot. Notes with Vim are synced to laptop and raspberry pi via Syncthing.
Websites for everything else. Trying to move off Gmail (already have for work, self-hosting now, was sending as my personal domain for years via Gmail/Apps) and the Google ecosystem. Already out of Facebook for a good while now. Still tweeting, but only work-related. Would like to play with Slack, but an N900 client is probably not in the works :)
Side-note, while explaining, I'm holding out for a decent (open, free) alternative to Maemo. That looks to me like Ubuntu Touch/Phone, especially with their convergence plans, but the dust might need to settle on that first. None of the Jolla/Sailfish/Firefox offers look quite like what I'm after yet, for various reasons. A nice polished Ubuntu phone would bring me up to date and out of the 5 years-ago past.
If that all comes to pass then the top-5 apps list might look something like:
Firefox/Iceweasel, email client, translation tools, Vim, SSH
Gmail, Hangouts (Android L SMS integration), Chrome, Sleep Better, reddit is fun.