Skittle is now available on SourceForge and will be updated regularly from there.  In order to keep a single version of Skittle current please refer to SourceForge for download:

Skittle Download 

Note: The zip file also contains an example FASTA file for viewing. It is the first million base pairs of Human Y Chromosome. It was chosen because it is exceptionally rich in repetitious DNA and forms many visually striking patterns.  

FASTA Files

To explore more genomes with Skittle you'll need FASTA files.  You can download FASTA files at:

UCSC Genome Browser Download 

Generally, the files named "chromFa" are the ones you'll want for Skittle.  For example the whole Human genome can be found at: http://hgdownload.cse.ucsc.edu/goldenPath/hg19/bigZips/chromFa.tar.gz  You'll need to decompress the original tar file until you get a series of .fa FASTA files, one for each chromosome.

Source Code 

Skittle is an open source project released under the GPL.  You are free to modify the source code and submit patches.  SourceForge uses an SVN checkout system.  For more information on obtaining the source code head to Skittle Developer's Page.