Your repositories allow you to keep up to date with software updates and bug fixes, get new versions, and easily install software when you become aware of it. Having a good repository setup is key.

YUM Plugins

There's no good reason why this is not default. It tells yum to search mirrors based on which one gives the fastest connection.

 sudo yum -y install yum-fastestmirror

Non-libre Software

RPMFusion

Necessary for mp3, dvd encryption, and software updates that are new or include binary or closed source components. Still free and legal, though.

 sudo rpm -Uvh http://download1.rpmfusion.org/free/fedora/rpmfusion-free-release-stable.noarch.rpm
 sudo rpm -Uvh http://download1.rpmfusion.org/nonfree/fedora/rpmfusion-nonfree-release-stable.noarch.rpm

Google

Necessary for picasa and future google programs.

sudo vi /etc/yum.repos.d/google.repo

[google64]
name=Google - x86_64
baseurl=http://dl.google.com/linux/rpm/stable/x86_64
enabled=1
gpgcheck=1
gpgkey=https://dl-ssl.google.com/linux/linux_signing_key.pub

[google]
name=Google - i386
baseurl=http://dl.google.com/linux/rpm/stable/i386
enabled=1
gpgcheck=1
gpgkey=https://dl-ssl.google.com/linux/linux_signing_key.pub

[Get Code]

Skype

sudo vi /etc/yum.repos.d/skype.repo

[skype]
name=Skype Repository
baseurl=http://download.skype.com/linux/repos/fedora/updates/i586/
enabled=1
gpgkey=http://www.skype.com/products/skype/linux/rpm-public-key.asc
gpgcheck=0

[Get Code]

Adobe

For adobe reader and etc., you should install them directly like you did RPMFusion.... but it's a bit buggy right now so I'm not suggesting how.