SharePoint Customization resources:

·         Work with Sharepoint Lists (Part 1):
http://office.microsoft.com/en-ca/assistance/HA011199881033.aspx

·         Working with Sharepoint Lists (Part 2):
http://office.microsoft.com/en-ca/assistance/HA011298651033.aspx

·         Creating Custom WebPart Page Templates (This covers more than just lists/webparts, but good resource overall):
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnspts/html/sharepoint_CreatingCustomWPPTemplates.asp

·         Custom WebParts sample code:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/odc_sp2003_ta/html/sharepoint_northwindwebparts.asp

 This whitepaper will also be very helpful:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/odc_sp2003_ta/html/sharepoint_northwindwebparts.asp