Package skype-2.1.0.81-fc.i586.rpm is not signed

Workaround:
/etc/yum.repos.d$ sudo mv skype.repo skype.repo.bak

Update:
$> sudo yum update

Putback:
/etc/yum.repos.d$ sudo mv skype.repo.bak skype.repo

/var is full and needs cleanup

Step 1: Determine which folder in /var is full (Clean /var)

$> sudo du -csh /var/*

Now you need to dive deeper to figure out the culprits.

Typically the /var/log may be full or contains a lot of log messages. Get rid of the large log files.

Step 2:If your /var/cache/yum is large/full and needs cleanup (Clean /var/cache/yum).

$> sudo yum clean packages

If this does not bring the size of the folder down.
$> sudo yum clean all

Step 3: If you have upgraded Fedora via preupgrade, then your /var/cache/yum/preupgrade folder is large. (Clean /var/cache/yum/preupgrade)

$>sudo rm -fr /var/cache/yum/preupgrade*