su -
## OR ##
sudo -i

## Remi Dependency on Fedora
rpm -Uvh http://download1.rpmfusion.org/free/fedora/rpmfusion-free-release-stable.noarch.rpm 
rpm -Uvh http://download1.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-stable.noarch.rpm
 
## Fedora 13
rpm -Uvh http://rpms.famillecollet.com/remi-release-13.rpm
 
## Fedora 12
rpm -Uvh http://rpms.famillecollet.com/remi-release-12.rpm
 
## Fedora 11
rpm -Uvh http://rpms.famillecollet.com/remi-release-11.rpm
 
## Fedora 10
rpm -Uvh http://rpms.famillecollet.com/remi-release-10.rpm
 
## Fedora 9
rpm -Uvh http://rpms.famillecollet.com/remi-release-9.rpm
 
## Fedeora 8
rpm -Uvh http://rpms.famillecollet.com/remi-release-8.rpm

yum --enablerepo=remi list thunderbird

Loaded plugins: changelog, fastestmirror, presto, refresh-packagekit
...
remi                                                            | 3.0 kB     00:00     
remi/primary_db                                                 | 106 kB     00:00     
Installed Packages
thunderbird.i686                        3.0.5-1.fc13                           @updates
Available Packages
thunderbird.i586                        3.1.7-1.fc13                           @updates

yum --enablerepo=remi update thunderbird
## OR ##
yum --enablerepo=remi install thunderbird

...
Setting up Update Process
Resolving Dependencies
--> Running transaction check
---> Package thunderbird.i586 0:3.1.7-1.fc13 set to be updated
--> Finished Dependency Resolution
 
Dependencies Resolved
 
=======================================================================================
 Package               Arch           Version                     Repository      Size
=======================================================================================
Updating:
 thunderbird           i586           3.1.7-1.fc13             updates            27 M
 
Transaction Summary
=======================================================================================
Install       0 Package(s)
Upgrade       1 Package(s)
 
Total download size: 27 M
Is this ok [y/N]: y
Downloading Packages:
Setting up and reading Presto delta metadata
Processing delta metadata
Package(s) data still to download: 27 M
thunderbird-3.1.7-1.fc13.i586.rpm                            |  27 MB     00:12     
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Warning: RPMDB altered outside of yum.
  Updating       : thunderbird-3.1.7-1.fc13.i586                                1/2 
 
WARNING : This thunderbird RPM is not an official Fedora build and it
overrides the official one. Don\'t file bugs on Fedora Project.
Use dedicated forums http://forums.famillecollet.com/
 
  Cleanup        : thunderbird-3.0.5-1.fc13.i686                                   2/2 
 
Updated:
  thunderbird.i586 0:3.1.7-1.fc13                                                   
 
Complete!