Some good articles / references / links :
Hope these articles help you in getting started . As always Jiri / Bunty are the go-to people for any queries related to custom components / references .
The above links are good.
I believe please read the document "the-definitive-guide-to-stellent-content-server-development.9781590596845.25034.pdf-revHEAD.svn000.tmp.pdf" to become an expert in custom component.