If you using unix, you can do something like this:

tar cvzf - mydir | split -d -b 2g - mybackup.tar.gz.
[download]

This will archive the contents of mydir, using gzip compression. The archive will be split into files having names like mybackup.tar.gz.00, mybackup.tar.gz.01, mybackup.tar.gz.02, etc. Each of these backup files will be no larger than 2 Gig.
You can unpack the archive like this:

cat mybackup.tar.gz.* | tar xvzf
[download]

For more info, read the man pages on tar and split.