Hi Chuk,
A good place to start is the SKILL Information page available from the Resources menu in Cadence Online Support which has a page of Custom IC SKILL Code Library. This contains a sampling of some SKILL code written by Cadence customer support - the functions meet certain coding standards and have been somewhat tested, but it is worth noting that these examples, and any other SKILL code, are not supported or warranted in any way, they serve mainly as an example.
I hope that this helps.
Best regards,
Lawrence.