Yes, the OPC Marketplace also allows to add trainings, development or consulting services. Just follow the same steps for adding new products except for choosing one of the service categories.
Also for services we expect that the details of the offered service is provided. For example when offering a training, the training class will have a scope which could include UA Profiles (Standard UA Server, Data Access, ...). In this case it is expected to provide the exact list of covered profiles, so visitors can use the OPC Marketplace to find services matching their needs. Just like for products.