To post the forums related to VMware vSphere APIs , please refer to vSphere Web Services SDK community: http://communities.vmware.com/community/developer/forums/managementapi?view=discussions
You might want to refer to http://communities.vmware.com/docs/DOC-11300 which would help you in understanding the basics of vSphere web services SDK.
You could also refer to C# sample Create.cs shipped with the vSphere SDK package, which lets you create a Folder and demonstrates the usage of CreateFolder API.
Hope the information is helpful.
- Angela -