Lorenzo @ atareao.es has created yet another Ubuntu indicator: Google Reader Indicator, which you can use to take a quick look at your unread Google Reader items.

CloudSN (Cloud Services Notifications) is an application similar to Specto (which is not maintained anymore): it can display notifications when you have new emails (POP3 and IMAP), new Identi.ca messages, Google Reader unread items or it can watch any RSS feed for changes.

Googsystray is a Google Voice, Gmail, Google Calendar, Google Reader and Google Wave checker application for Windows and Linux. The idea is to be able to keep track of all that stuff without having to keep a bunch of browser tabs open, or constantly checking them.