Is there a .NET API for OpenOffice?
EDIT: Is there a OpenOffice SDK for .NET?
Novel has a branch of OOo that adds mono capabilities, so you can use these builds for scripting via .Net inside OOo. The document formats for OOo (except for Base) is XML + resources in a zip container. If you need programmatic access beyond manual file manipulation, your best bet is to use the ActiveX control with COM Interop. If you want to use Base as a datasource in .Net, it is near impossible, as it's an embedded Java database structure without a mature .net port.