Anyway, if you've installed Ubuntu 11.04 and looking for a plugin that "notifies" you that runs in the Unity-Launcher when new messages arrives without being annoying... then there is a separate plugin for Pidgin that integrates with the new "libappindicator" protocol in Natty Narwhal.
So if you want to give it a try then open your Terminal and issue the below command.
sudo add-apt-repository ppa:jfi/pidgin
sudo apt-get install pidgin-libnotify
Update: Please take into account that, Pidgin (the main "engine" behind pidgin-libnotify) stores your passwords in a plain text file!. So anyone who can access your account can easily read your account information.
But when I was reading the original Pidgin developer's explanation concerning this... it seems that almost all the major online chat clients does this!. For some reason IM protocols makes it hard for the client apps to secure their passwords or sensitive data by using encryption method. So, be aware of that, and again... you really can't just blame Pidgin since a lot of major IM clients do this.
The above developers post it a bit old actually, but what it says is true to this day (yep... still password = plain text :( ). Below is a portion of that page that I pasted so you could get an idea (seriously, go and read that above link.. it explains it in much better details).
Question:"Is that the final word?"
No. The Pidgin developers are generally open to, and would encourage integration with keyrings. A keyring is an implementation of the first bullet point above. It would be used to cryptographically secure your password in a way that would generally be more secure (although not perfect). It would require a master password, shared amongst all the applications on your computer, to get at your passwords.
If someone were to do this in a way that worked well, securely, and seamlessly to the user, without interfering with people who prefer to trust their file system's security, we'd gladly accept it.