CloudSN (Cloud Services Notifications) is an application you can use to 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 (which means you can use it for Facebook too). For a complete review, see our previous post on CloudSN.
Back when Twitter introduced OAuth for all applications, CloudSN stopped working with Twitter but an update finally brings Twitter OAuth support for CloudSN.
The new version is available in the CloudSN PPA for Ubuntu 10.10 Maverick Meerkat (only!) - add the PPA and install CloudSN using the following commands:
sudo add-apt-repository ppa:chuchiperriman/cloudsn sudo apt-get update sudo apt-get install cloudsn
Once installed, run it from Applications > Internet > Cloud Services Notifications.