There are several CPAN modules to generate tag clouds. To cite only 3 of them:

• HTML::TagCloud
• HTML::TagClouder
• Data::CloudWeights

I just added tags cloud on this site (look the new home page!) with Data::CloudWeights. HTML::TagCloud generate ugly HTML and CSS that cannot be modified. HTML::TagClouder is marked as *WARNING* Alpha software! I mean it! Not for me, thanks!

Data::CloudWeights is far the most flexible. It generates an arrayref of hashes from which you can pick size, occurences, colors and so on. I use the following subroutine to generate the cloud with a very simple and standard code:

use Data::CloudWeights;
sub tag_cloud {
	my @tags = @_;
	my $cloud = Data::CloudWeights->new;
	for my $tag (@tags) {
		# The followin line is a bit more complicated than shown here
		# $tag is a DBIx::Class entry with more columns than displayed here
		$cloud->add($tag->tag, scalar  $tag->links, "/tag/" . $tag->tag);
	}
	my $cloud_html = "";
	foreach my $tag (@{$cloud->formation}) {
		$cloud_html .= '<a href="' . $tag->{'value'} .
			'" style="font-size: ' . $tag->{'size'} . 'em">';
		$cloud_html .= $tag->{'tag'};
		$cloud_html .= '</a>';
	}
	return $cloud_html;
}