I'd prefer a commercial solution. So not NHibernate. Now i'm playing with LLBLGen pro and i like it but it doesn't seem be DDD friendly.
Mindscape's LightSpeed O/R Mapper was built with DDD in mind from the beginning.
If by "DDD friendly" you meant that the ORM supports concepts and patterns such as Entities and Value Objects, Unit of Work, Repository, Specification and Aggregates then certainly LightSpeed uses these.
The other comments are valid however - could you define DDD friendly in more detail please? I'm also sure that most modern ORMs support at least some of the aspects that I've highlighted here.
Try DataObjects.Net, it automatically generates database schema from model classes and allows to work with domain model, rather than with database. I think it is pretty good for DDD.
Try ECO. It is commercial but is free to try and unlimited use up to 12 classes. And you can do a lot with 12 classes. It has reached version 5 so it is mature.
NHibernate now has commercial support and would be my recommendation - you can start object first and it has LINQ support now that LINQ to NHibernate is 1.0
Works with SQL Server/Oracle/DB2/etc