There are at least four types of validation you could do with an RDF document which might be useful (quite apart from XML and RDF well-formedness validation which The RDF validator at W3C does):
The last two of these are something that schemarama might be able to do; I've had a stab at the others here, also building in some best practice advice for FOAF files, as an example. See Missing isn't broken: data validation and freedom on the Semantic Web to see some caveats about validation of RDF documents, and references for previous work in this area; also there are some bugs/ommissions.
Although FOAF is used in the example below, the tool should work with any RDF schema, and is intended to be generic. Please note that this is an experimental service. Comments, bugs etc to firstname.lastname@example.org.
This is useful way of looking at your schema, for checking that you wrote what you thought you wrote.schema url: