I\'ve just started using Linq to SQL, and I\'m wondering if anyone has any best practices they can share for managing dbml files.
Have you looked at SqlMetal? It's officially supported, although not promoted too much. You can use it to build dbmls from the commandline - we've used it as part of a db's continous integration updates (make sure you have really good code separation if you do this though - partial classes are a saviour - as the dbml will get overwritten).
If I recall correctly it doesn't have quite the same features as the model designer in Visual Studio (I think it handles pluralisation differently). There a good post about it on Ben Hall's blog.