Is there any documentation on how to add a new Dialect?

I'm trying to add one; I compiled the dialect code into its separate jar (and put it in the classpath) but Hibernate still can't find it. But when I build the hibernate3.jar (with the dialect inside) myself; hibernate finds it.

I thought adding dialects should be as simple as dropping in a jar as long as I extent/implement appropriate classes; is that not so?

You've got to use the hibernate.dialect property.
Trying to discover classes implementing/extending a class based on what's available on the classpath is usually not feasible/not a good idea.

Yes I have set the hibernate.dialect property and I am asking it to pick the new dialect and I am still seeing the exception.

What exception are you seing ?
I think your problem is more classpath related than Hibernate related.

I resolved this.

I wrote a test class and did a Class.forName("dialect-name") and found that the class loader was complaining about one of the manifest entries within the dialect jar.

I changed the manifest entry and it worked after that. The manifest entry contained illegal characters like '/' and a space.

The exception I was getting from hibernate was not telling me what exactly was wrong. Only when I tried to load the class explicitly I knew what was wrong.