From MSB Software Engineering:
Relation helps you document your Microsoft Access databases by creating 'Entity Relationship Diagrams'. Just open an MDB-File, choose some, or all tables and when they pop onto the screen move the lines and tables around to make it look nice. Then add a couple of other text and drawing objects including embedded OLE objects to make it look really cool. Save, print and impress your boss.
The diagrams can be re-synchronized with the database as you make changes to the tables, fields and relationships with Access.